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The newborn period marks a time when red blood cell (RBC) indices change significantly. Anemia can occur at various times in the neonatal period, from the perinatal and immediate postnatal period through the first months of life. Hematocrits 2 or more standard deviations below the normal range for gestation are seen frequently and should be evaluated. Conversely, true anemia, the inability to adequately deliver oxygen to tissues, is less common. Anemia can be classified into the following 3 major processes: hemolysis, hemorrhage, or hypoproliferative disease. Anemia can also result from overlapping processes. For example, sepsis can result in hemolysis, disseminated intravascular coagulation (DIC), and subsequent hemorrhage. This chapter reviews fetal and neonatal erythropoiesis, discusses the etiology and diagnosis of anemia in the neonatal period, and offers management options for anemic term and preterm infants.
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The growth factors stimulating fetal erythropoiesis during gestation are produced solely by the fetus. Erythropoietin, or Epo, is the primary growth factor responsible for erythropoiesis after birth and appears to be the principal growth factor for fetal erythropoiesis as well. Primary production of Epo occurs in the liver during fetal development. The kidney becomes the primary source of Epo following delivery; however, the etiology for the liver-to-kidney switch continues to be studied. Anephric fetuses have normal serum Epo concentrations and normal hematocrits, proving that renal Epo production is not required for erythropoiesis during fetal development. Methylation patterns in the promoter and enhancer regions of the Epo gene isolated from fetal liver and kidney suggest increased methylation in the kidney as a possible explanation for decreased Epo gene expression during fetal development.
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During gestation, the site of red cell production transitions from yolk sac to liver to marrow. Primitive erythroblasts are produced in the fetal yolk sac during the first 3–4 weeks of gestation. By 6 to 8 weeks’ gestation, definitive erythropoiesis is established in the fetal liver. Although erythrocytes are noted in the fetal marrow as early as 8–9 weeks’ gestation, the liver remains the primary site of erythropoiesis until well into the second trimester. By the third trimester, erythropoiesis occurs primarily in the fetal marrow, although production can continue in extramedullary sites in the face of increased need, during times of hemolysis, or in fetal infection caused by a variety of bacteria or viruses.
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Variations in hematologic indices for preterm and term infants reflect the dynamic nature of the erythron in late fetal development. The production of hemoglobin transitions from embryonic (Gower 1 [ζ2ε2], Gower 2 [α2ε2], and Portland [ζ2γ2]) to fetal hemoglobin (α2γ2) and finally to adult hemoglobin (α2β2), as shown in Figure 31-1.
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In conjunction with changes in globin gene expression and the transition from embryonic to fetal hemoglobin production, hemoglobin concentrations gradually increase, from approximately 14.5 g/dL at 28 weeks’ gestation to 15 g/dL at 34 weeks to 16.8 g/dL at 40 weeks.1 The relationship between cord hemoglobin concentration and duration of pregnancy is linear for infants who are appropriate for gestational age (AGA). The mean corpuscular volume (MCV) is higher in preterm infants than in term infants and is inversely proportional to gestation, averaging 5–20 fL higher than the mean MCV of 108 fL in term infants.
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Reticulocyte counts are elevated at birth, averaging 6% to 10%. Nucleated red blood cells (NRBCs) are not consistently elevated, but there does appear to be an inverse relationship between number of NRBCs and gestational age. Normoblasts are cleared rapidly from the circulation during the first postnatal days, although a few may still be observed in small preterm infants into the second week of life. Variations in red cell size and shape are somewhat greater than those observed in term infants.
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Neonatal Erythropoiesis
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The abrupt transition from the relatively hypoxic in utero environment to the oxygen-rich postnatal environment triggers erythropoietic responses that have a profound effect on the red cell mass. Over the first 2 to 6 months of life, the infant experiences both the highest and the lowest hemoglobin concentrations occurring at any time in development. Although variable, Epo levels at birth are above the normal adult range but decrease abruptly in the immediate postnatal period, with a half-life of no more than 4 hours (2.6 ± 0.5 hours in infants with polycythemia and 3.7 ± 0.9 hours in infants born to mothers with preeclampsia.)2 By 24 hours, the Epo value is nearly undetectable and remains so throughout the first month of life. The decrease in Epo is accompanied by a decrease in the number of erythroid progenitors and in the reticulocyte count.3
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A combination of decreased red cell production, shortened cell survival, and growth-related expansion of the blood volume results in a progressive fall of the hemoglobin concentration to a mean of approximately 11 g/dL at 2–3 months of age.1 The lower range of normal for infants of this age is approximately 9 g/dL. This nadir is called physiologic anemia, in that it is not associated with lack of oxygen delivery to tissues and is not abrogated by nutritional supplements. Stabilization of the hemoglobin concentration is heralded by an increase in reticulocytes in the second month of life. Thereafter, the hemoglobin concentration rises to an average of 12.5 g/dL, where it remains throughout infancy and early childhood.
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Hemolysis is the premature destruction of erythrocytes and is generally categorized as immune-mediated or non-immune-mediated hemolysis (Table 31-1). Immune-mediated hemolysis occurs when immunoglobulin (Ig) G antibodies created by the maternal immune system cross the placenta and cause destruction of antigen-containing fetal red cells (isoimmunization). Hemolysis in the fetus can be severe enough to lead to hydrops fetalis. Non-immune-mediated hemolysis occurs when intrinsic abnormalities in the fetal or neonatal red cell lead to premature destruction and a shortened red cell life span.
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In older children and adults with congenital hemolytic anemia, there is usually clear evidence of hemolysis, as manifested by indirect hyperbilirubinemia, reticulocytosis, and low haptoglobin levels, all markers of increased red cell destruction. In neonates, however, the recognition of congenital hemolytic anemia utilizing these laboratory measurements is more challenging. Physiologic indirect hyperbilirubinemia is common in neonates because of the increased red cell mass at birth, decreased RBC survival, and reduced hepatic glucuronyl transferase activity. Also, the normal physiologic anemia of infancy can modulate reticulocytosis in the presence of mild hemolytic anemia. Finally, serum haptoglobin is not a reliable index of neonatal hemolysis because concentrations of this protein do not increase until after 6 months of age.
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Neonates with congenital hemolytic anemia may have a normal-for-age hemoglobin or there may be mild-to-severe anemia. Indirect hyperbilirubinemia presenting earlier than expected and in excess of the usual physiologic levels is the most common and occasionally only sign of hemolytic anemia. Reticulocytosis and persistence of nucleated RBCs beyond the third day of life are other reasons to evaluate a neonate for hemolytic anemia. Acquired hemolytic anemia in neonates occurs with alloimmune hemolysis (chapter 34), hemolytic anemia secondary to maternal disease, and hemolysis secondary to infection or microangiopathic anemia.
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Immune-Mediated Hemolysis
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The most common cause for hemolysis in the neonatal period is immune-mediated hemolysis due to ABO incompatibility or Rh incompatibility. Following the advent of RhoGAM (RhD antibody), the incidence of hydrops fetalis due to RhD sensitization decreased significantly, from approximately 1 in 200 live births to now less than 1 in 1000 live births.4 Immune-mediated hemolysis due to anti-A or anti-B antibodies crossing the placenta is now the most common etiology of immune-mediated hemolysis.
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RhD Isoimmunization: RhD incompatibility occurs when a woman with RhD-negative blood type is exposed to Rh-positive blood cells, leading to the development of RhD antibodies (anti-D antibodies). Fifteen percent of the population lacks the D antigen (is Rh negative). RhD sensitization occurs in approximately 1 per 1000 births to women who are Rh negative.
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RhD incompatibility occurs through 2 primary mechanisms. The most common route of exposure occurs when an Rh-negative pregnant mother is exposed to Rh-positive fetal RBCs secondary to fetomaternal hemorrhage (FMH), spontaneous abortion, or normal delivery. RhD incompatibility can also occur if an Rh-negative female accidentally receives Rh-positive blood. Maternal anti-D IgG antibodies freely cross the placenta into the fetal circulation, where they form antigen-antibody complexes with RhD-positive fetal RBCs. The red cells are eventually lysed, leading to isoimmune hemolytic anemia.5 As a result, large amounts of bilirubin are produced from the breakdown of fetal hemoglobin and are transferred via the placenta to the mother, where they are conjugated and excreted.
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Once the baby is born, low levels of glucuronyl transferase can lead to significant elevations of unconjugated hyperbilirubinemia. Erythroblastosis fetalis is a severe form of the disease characterized by severe hemolytic anemia and hydrops fetalis, involving placental and fetal edema, ascites, pericardial effusion, high-output cardiac failure, and extramedullary hematopoiesis. The risk and severity of sensitization increase with each subsequent pregnancy in which the fetus is Rh positive. The risk of sensitization depends on the volume of FMH, the extent of maternal immune response, and the concurrent presence of ABO incompatibility, which actually decreases the severity of hemolysis in Rh-positive fetuses.
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Administration of RhoGAM decreases the production of maternal IgG antibodies by inhibiting immune memory. RhD immune globulin coats the surface of RhD-positive fetal RBCs. These antibody-antigen complexes inhibit the stimulation of maternal B cells to produce IgG antibodies. RhoGAM is administered once at 28–32 weeks’ gestation. It has a short half-life of 23–28 days and is thus administered again within 72 hours after delivery. Rh-negative (nonsensitized) women presenting to the emergency room with antepartum bleeding or potential FMH should receive 300 μg of Rh IgG.6 An additional 300 μg of Rh IgG should be administered for every 30 mL of fetal blood to which the Rh-negative mother is exposed. A lower 50-μg dose (MICRhoGAM) is available and recommended for Rh-negative women who have a termination of pregnancy in the first trimester when the volume of FMH is likely minimal.7
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ABO Isoimmunization: Hemolysis of fetal red cells caused by ABO antibodies occurs almost exclusively in infants of blood group A or B who are born to group O mothers.8 Anti-A and anti-B antibodies formed in group O individuals are mainly IgG antibodies and thus can cross the placenta, whereas anti-A and anti-B antibodies found in the serum of group A or group B individuals tend to be IgM antibodies. ABO incompatibility tends to be relatively mild in nature, mainly because fetal RBCs do not express adult levels of A and B antigens, resulting in few reactive sites. This allows the antibody-coated cells to remain in the circulation for a longer period of time compared to RhD disease. In addition, severity of ABO incompatibility is not dependent on birth order.9
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The presence of microspherocytes on peripheral blood smear is a characteristic of ABO isoimmunization, with little or no increase in nucleated RBCs. In RhD isoimmunization, there are fewer spherocytes and a large number of nucleated RBCs.10 ABO isoimmunization usually presents with hyperbilirubinemia and can be managed by phototherapy alone. Exchange transfusions are occasionally required. The direct antiglobulin test (DAT) is usually weakly positive but can be negative in some cases despite evidence of immune-mediated hemolysis.
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Minor Blood Group Isoimmunization: Although RhD isoimmunization is the most common cause of severe hemolytic disease of the newborn, other antibodies belonging to Kell (K and k), Duffy (Fya), Lewis, Kidd (Jka and Jkb), and MNSs (M, N, S, and s) systems can cause severe hemolytic disease of the newborn.11 Kell antigen is a minor blood group antigen that often results in isoimmunization. In addition, antibodies directed against Kell antigens can bind to erythroid progenitors in the fetal marrow and result in hypoproliferative anemia.12 Minor Rhesus blood group antigens c and E can also cause severe hemolysis, requiring exchange transfusion.
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Non-Immune-Mediated Hemolysis
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Glucose is the major metabolic substrate for RBCs, and it is metabolized via the glycolytic pathway and hexose monophosphate (HMP) shunt. The glycolytic pathway generates adenosine triphosphate (ATP), NADH (reduced nicotinamide adenine dinucleotide), and 2,3-disphosphoglycerate (2,3-DPG), all important in maintaining RBC integrity. The HMP shunt pathway is critical for protecting RBCs against oxidative insult. Glucose-6-phosphate dehydrogenase (G-6-PD) is the initial step in the HMP pathway. Among hemolytic anemias due to hereditary enzyme deficiencies, G-6-PD deficiency is the most common. The remaining glycolytic pathway enzymopathies are relatively rare, with only a few thousand cases known and 90% due to pyruvate kinase deficiency.
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Glucose-6-Phosphate Dehydrogenase Deficiency: Deficiency of G-6-PD is one of the most common genetic disorders in the world, affecting over 400 million people worldwide.13 It is a sex-linked disorder affecting males, but females who are homozygous for G-6-PD deficiency or have skewed lyonization of the X chromosome can also have significant enzyme deficiency. This enzymopathy is found most commonly in people from Africa, Asia, and the Mediterranean region. Three clinically important types of G-6-PD deficiency are classified by the World Health Organization (WHO). Class I G-6-PD deficiency is vanishingly rare, but it is the most severe form, characterized by lifelong mild-to-moderate chronic hemolytic anemia. Class II G-6-PD variants, commonly found in Mediterranean (G-6-PDMediterranean), Middle Eastern, and Asian people, have a marked enzyme deficiency that is associated with severe anemia after exposure to oxidant drugs and chemicals (eg, primaquine, ciprofloxacin, nitrofurans, sulfonamides, dapsone, naphthalene) or fava beans. Class III G-6-PD is the mildest deficiency, found in people of African (A-variant) and Asian background who experience moderate but self-limited hemolytic anemia with oxidant exposure. In patients with class II or III G-6-PD, there is no anemia or hemolysis in the steady state when there is no oxidant exposure.
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G-6-PD deficiency in neonates is associated with high risk of severe jaundice and kernicterus.14, 15 It is much more common in neonates with class II variants than in infants with class III G-6-PD deficiency. The possibility of G-6-PD deficiency should be considered in infants with hyperbilirubinemia beyond expected physiologic levels. The neonatal jaundice associated with G-6-PD deficiency has a late peak at day 5–6 of life; it may be especially difficult to identify in preterm infants due to their later peak bilirubin levels. Of particular importance, hyperbilirubinemia often is the only abnormality, and there may be no other signs of hemolysis. This observation has suggested that hyperbilirubinemia might not be related solely to increased bilirubin production from red cell destruction but rather may be due to a defect in liver clearance of bilirubin.16 Also, there are reports suggesting that marked hyperbilirubinemia in G-6-PD deficiency is associated with the simultaneous inheritance of the variant Gilbert polymorphism.17 In the United States, severe hyperbilirubinemia due to G-6-PD deficiency is responsible for over 30% of kernicterus cases.18 Neonates at risk for G-6-PD should have bilirubin levels measured prior to discharge. Close outpatient follow-up is particularly important given that many neonates are discharged early from the hospital. Neonatal discharge guidelines have been established by the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists.19
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Severe hyperbilirubinemia occurring in G-6-PD deficiency requires phototherapy and, occasionally, exchange transfusion. Packed RBC (PRBC) transfusion should be given for symptomatic anemia. Avoidance of oxidative medications and chemicals is important to prevent further hemolysis. Mothers who are breastfeeding should be counseled to avoid ingestion of fava beans and oxidant medications. Vitamin K injection is safe for neonates with class II and III variants and should be given to prevent hemorrhagic disease of the newborn.
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Pyruvate Kinase Deficiency: Pyruvate kinase (PK) deficiency is the most common glycolytic pathway defect. Over 200 different mutations of the 2 different PK genes (PKM2 and PK-LR) have been reported.20 It is an autosomal disorder, with most patients compound heterozygous for 2 different mutations. The prevalence of PK deficiency among Caucasians in the United States has been estimated at 1 in 20,000. The disease is common among the Amish population in Pennsylvania and other inbred communities.21
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Pyruvate kinase catalyzes the conversion of phosphoenolpyruvate to pyruvate, at the same time generating ATP, a critical source of energy for RBCs. Impaired ATP production occurs in PK-deficient cells, leading to loss of membrane plasticity and, ultimately, splenic destruction of red cells.
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The clinical features of PK deficiency are highly variable, ranging from severe anemia and jaundice at birth to an incidental finding in adults. This is likely related to the many different known mutations and the often-compound heterozygosity for different mutations causing the deficiency.
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Deficiency of PK should be part of the differential diagnosis of hydrops fetalis and neonatal jaundice. Jaundice can be pronounced, and kernicterus has been reported.22 In contrast to G-6-PD deficiency, in addition to hyperbilirubinemia, there are usually obvious features of hemolysis, including anemia and reticulocytosis. PK deficiency should be suspected in a neonate with evidence of hemolytic anemia after immune-mediated hemolysis, hereditary spherocytosis (HS), and G-6-PD deficiency are ruled out.
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Hyperbilirubinemia should be managed with phototherapy and exchange transfusion as needed. Severe anemia may require red cell transfusions to maintain hemoglobin or as needed to maintain normal neonatal growth and development. Many children with severe PK deficiency are transfusion dependent until they undergo splenectomy after 5 years of age.
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Other RBC Enzymopathies Associated With Hemolysis: Abnormalities have been reported in all glycolytic enzymes. These conditions are rare, accounting for less than 1% of hemolytic anemia due to enzymopathies.23 After PK deficiency, which accounts for 90% of glycolytic enzymopathies, glucose phosphate isomerase (GPI) deficiency is the next most common. All glycolytic enzymopathies are associated with chronic nonspherocytic hemolytic anemia. The degree of hemolytic anemia varies from mild to severe, and hydrops fetalis has been seen in those with the most severe hemolysis. Several glycolytic enzyme deficiencies are associated with myopathy or neurologic deficits. Most are inherited in an autosomal recessive (AR) pattern except phosphoglycerate kinase deficiency, which is X linked. This group of rare disorders should be considered when a neonate shows clear and persistent evidence of nonspherocytic hemolytic anemia and after other hemolytic causes such as immune-mediated hemolysis, membrane defects, and the more common enzymopathies discussed have been ruled out. Enzymopathies should also be considered in neonates with neurologic defects or myopathy in addition to hemolytic anemia. Specific assays of RBC enzyme activity are necessary for diagnosis of these rare conditions. In some cases, DNA-based molecular tests are available.
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Hemolytic anemias due to abnormalities of the erythrocyte membrane comprise an important group of inherited disorders. The most common disorder encountered is HS. Hemolysis due to hereditary elliptocytosis (HE), and the hereditary stomatocytosis (HSt) syndromes also occurs but is less common.
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Hereditary Spherocytosis: Hereditary spherocytosis is the most common hereditary hemolytic anemia in people of northern European descent, occurring in up to 1 in 2500 individuals.24 In the United States, it is estimated that 1 in 5000 people have HS. Most cases of HS are inherited in an autosomal dominant (AD) pattern. However, up to 25% of cases do not display this inheritance; some are new mutations, while others represent AR inheritance.
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Hereditary spherocytosis is associated with deficiencies of membrane cytoskeleton proteins (spectrin, ankyrin, or band 3) that lead to destabilization of the RBC lipid bilayer, resulting in progressive membrane surface loss and microspherocyte formation.25 Microspherocytes are vulnerable to entrapment by the spleen, which leads to further membrane loss and ultimately cell destruction by splenic macrophages. A characteristic feature of HS is the presence of spherocytes seen in the peripheral blood smear. However, even normal neonates can have a small population of spherocytes, and as noted previously, spherocytes also are found in neonates with hemolysis due to ABO incompatibility. Older children and adults with HS commonly have anemia, reticulocytosis, indirect hyperbilirubinemia, and splenomegaly.
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In neonates, the most common presentation of HS is jaundice. Jaundice may present early, be more severe than usual, persist longer, and may require treatment with phototherapy. Infants with HS rarely require an exchange transfusion. Up to 50% of adults with HS have a history of jaundice during the first week of life.26 Those who coinherit HS and the gene for Gilbert syndrome may develop marked jaundice requiring phototherapy.
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The diagnosis of HS can be made in a neonate with a positive family history of HS who has evidence of hemolytic anemia, the presence of an increased number of spherocytes on peripheral smear, elevation of mean corpuscular hemoglobin concentration (MCHC), and a negative DAT. In these cases, further testing is not necessary. However, if the family history is in doubt or if there is coexistence of ABO incompatibility, further testing of the neonate or repeat testing of the affected family member might be necessary to confirm the diagnosis. The incubated RBC osmotic test is used to detect spherocytosis. However, it is important to recognize that this test does not differentiate the various causes of spherocytosis. If there is an ABO incompatibility setup, it is important to obtain a DAT. Occasionally, the establishment of the diagnosis of HS needs to be delayed until confounding factors (maternal antibodies, fetal RBC changes) are resolved. Since management and counseling of neonates with hemolytic anemia is not dependent on the exact cause, the complete laboratory workup can usually be deferred for 4 to 6 months.
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Occasionally, severe symptomatic anemia can develop soon after birth and require a PRBC transfusion. More often, anemia develops after discharge from the nursery. It therefore is important to have close follow-up of these infants. While some neonates do not develop significant anemia at all, others may need PRBC transfusions during the first few months of life. Splenectomy is the definitive treatment of HS; however, even in the most severe cases, this surgery is often delayed until a child is at least 5 years old given the increased risk of life-threatening sepsis with encapsulated organisms in young children.
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Hereditary Elliptocytosis: The HE syndromes are a heterogeneous group of disorders characterized by the presence of elliptical-shape RBCs in the peripheral blood smear.
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Common HE is a dominantly inherited condition characterized by many elliptocytes in the peripheral blood smear. The clinical severity of common HE is extremely variable, ranging from an incidental asymptomatic condition, most commonly observed, to mild-to-moderate hemolytic anemia. The clinical expression of hemolytic HE ranges from a moderate hemolytic disorder to a severe, near-fatal or fatal hemolytic anemia. Hereditary pyropoikilocytosis (HPP) is a severe hemolytic anemia, with red cell fragments, poikilocytes, and microspherocytes seen on peripheral blood smear. From a clinical perspective, it is difficult to distinguish severe hemolytic HE from HPP. Once regarded as a separate condition, HPP is now recognized to be a variant of the HE disorders. Spherocytic HE is a rare condition in which both ovalocytes and spherocytes are present on the blood smear. Southeast Asian ovalocytosis (SAO), also known as stomatocytic elliptocytosis, is an HE variant prevalent in the malaria-infested belt of Southeast Asia and the South Pacific, and it is characterized by rigid spoon-shaped cells that have either a longitudinal slit or a transverse ridge. The varied clinical and hematologic manifestations of HE are an expression of the numerous molecular defects that give rise to an elliptocytic-shape erythrocyte. The most commonly encountered cases seen are nonhemolytic common HE, hemolytic HE, and HPP.
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The incidence of HE is estimated at 1:2000–4000 in the United States.27 It is found worldwide but is more common among people of African and Mediterranean decent. HE is inherited in an AD fashion. Heterozygous patients generally have asymptomatic elliptocytosis (common HE) that is often found incidentally. Overall, only 12%–15% of patients with HE are symptomatic at some time during their life.27
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Similar to HS, this membrane disorder is due to qualitative and quantitative defects of RBC membrane cytoskeletal proteins. Alternation in the amount, function, and structure of these proteins leads to elliptocyte formation, instability of the RBC membrane, and in some cases hemolysis. In the last subset of HE patients, symptoms include anemia, splenomegaly, and intermittent jaundice.
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Most neonates with HE are asymptomatic. However, infants with rare HE subtypes (common HE with infantile poikilocytosis and HPP) may present with severe hemolytic anemia. These neonates present with jaundice, moderate-to-severe anemia, and peripheral blood smear findings of marked poikilocytosis. In the neonatal period, common HE with infantile poikilocytosis and HPP are clinically indistinguishable. However, the poikilocytosis and severe hemolytic anemia are transient in patients with common HE. The distorted RBCs noted at birth morph into the typical HE elliptical shape by a few months of life, and there is complete resolution of the hemolytic anemia. At birth, it is difficult to predict if an infant has common HE or HPP. Hydrops fetalis has been described in association with unusually severe hemolytic HE.
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Children with common HE have anywhere from a few up to all elliptocytic RBCs on their peripheral blood smear. However, these elliptocytes usually do not appear until 4–6 months of age, so infants who present to the neonatal units generally have severe hemolytic anemia with poikilocytosis. In all cases, however, infants with hemolytic HE need to be followed to see if their elliptocytosis persists or benign common HE evolves. In the hemolytic variants seen in infants, the peripheral smear may demonstrate red cell fragments, microspherocytes, and some elliptocytes. Osmotic fragility testing in these patients is abnormal, with increased fragility. In addition to typical features of hemolytic anemia, the MCV of those with HPP can be very low (25–75 fL) due to the presence of a large number of microspherocytes.
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The management of neonates with hemolytic anemia due to HE is identical to any patient with hemolytic anemia. Most neonates require no treatment, but some may have significant hyperbilirubinemia and anemia requiring phototherapy, exchange transfusion, or PRBC transfusion. Splenectomy later in childhood is helpful in minimizing or resolving the chronic hemolytic anemia in those with severe hemolytic HE or HPP.
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Hereditary Stomatocytoses (HSt): HSt syndromes are a group of inherited disorders characterized by erythrocytes with a mouth-shaped (stoma) area of central pallor on peripheral blood smear. HSt is associated with abnormalities in red cell cation permeability that lead to changes in red cell volume. MCV may be increased (hydrocytosis), decreased (xerocytosis), or in some cases, near normal.28 Many patients present with hemolytic anemia in the neonatal period. Pallor, jaundice, hepatosplenomegaly, and signs of gallstone disease (in older patients) are the most common physical findings. Peripheral blood smears show an increased number of stomatocytes (up to 3% is normal). The reticulocyte count is elevated during hemolysis, and the stomatocytes are osmotically fragile in the overhydrated form of stomatocytosis and are resistant to osmotic lysis in the dehydrated form. Neonates with HSt may require phototherapy and occasionally exchange transfusions. Patients with HSt do not generally require splenectomy as the results vary. There is an increased risk of life-threatening thrombosis after splenectomy.29 Cholecystectomy may be considered in patients with cholelithiasis.
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Erythrocyte Hemoglobin Abnormalities
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Hemoglobin is a tetrameric protein made up of 4 globin chains, each associated with a heme group. The production of globin chains is directed by the alpha (α) gene cluster on chromosome 16 and the beta (β) gene cluster on chromosome 11. The α-gene cluster contains the embryonic delta (ζ) gene and 2 adult α genes. The β-gene cluster contains the embryonic epsilon (e) gene, the fetal gamma (γ) gene, and the adult β gene. During fetal development, embryonic globin production is switched to fetal or adult globin production at different times (ζ → α, e → γ, and γ → β). Various globin chains form different hemoglobin tetramers during embryonic, fetal, and postnatal life (Figure 31-1). Embryonic hemoglobins (Hb Gower 1, Hb Gower 2) are responsible for oxygen delivery during the first 8 weeks of gestation. By 10 weeks, embryonic chain production ceases, γ-chain synthesis ensues, and fetal hemoglobin (HbF: α2γ2) becomes the dominant hemoglobin. HbF has a high oxygen affinity, allowing the fetus to extract oxygen across the placenta. At term, 60%–90% of hemoglobin in a newborn is HbF. Following birth, γ-chain production is replaced by β-chain synthesis. By 6 months of age, 95% of hemoglobin will be adult hemoglobin (HbA), which is composed of 2 α and 2 β chains (α2β2). At birth, production of δ chains begins. The presence of HbA2 (α2δ2), a minor hemoglobin, increases gradually to the adult level of 2%–3% during the first few months of life.
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Congenital hemolytic anemias can be secondary to deficient production of normal hemoglobin (thalassemia syndromes) or production of abnormal hemoglobins (sickle cell disease). The α-globin chain disorders are manifest at birth, while β-globin chain abnormalities may not be clinically apparent until 4–6 months of age, after the switch from γ- to β-globin chain synthesis. Rare mutations affecting γ-globin chains also exist, and these can result in transient neonatal problems that resolve by 3 months of age.
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Thalassemia Syndromes: Thalassemia disorders are due to decreased production of normal α- or β-globin chains, leading to a relative excess of the complementary unaffected globin chains. Thalassemias are one of the most common genetic disorders worldwide. Just like G-6-PD deficiency and sickle cell anemia, it is believed that thalassemia heterozygosity is protective against malaria. In the United States, the large influx of Southeast Asian people has led to a significant increase in the number of thalassemia syndromes seen in this country. Newborn screening programs for sickle cell disease also have led to discovery of nonsickling hemoglobinopathies, including thalassemia.
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α-Thalassemia Disorders: These conditions are due to decreased or absent α-globin synthesis, a consequence of deletions or mutations of α-globin genes. More than 40 different deletions have been identified.30 Most commonly, α thalassemia occurs in China and Southeast Asia and less frequently in India, Kuwait, the Middle East, Greece, Italy, and northern Europe. In African Americans, α-thalassemia trait is common, with up to 5% prevalence, but it rarely causes clinically significant problems. With increasing immigration to the United States from countries with high carrier rates of thalassemia, the prevalence of significant α thalassemia is rising. Data from the California newborn program, a state with a 13% Asian population, suggest that the prevalence rate of α-thalassemia disorder is 1/9000.31
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Decreased α-globin chain production is associated with accumulation of the non-α-globin chains, leading to the formation of γ4 tetramers (Hb Bart) and β4 tetramers (HbH). The amount of Hb Bart or HbH will vary, depending on the number of α-globin genes deleted and the age of the patient.
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The silent carrier state is due to deletion of one α-globin gene. There are no clinical symptoms, and the blood counts are normal.
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The α-thalassemia trait is due to deletions of 2 α-globin genes. These individuals have no clinical symptoms but will have microcytosis, hypochromia, and mild anemia with a normal hemoglobin electrophoresis. At birth, the MCV is less than 100 fL, and the Hb Bart level is 2%–10% (normal is 1%). Beyond infancy, Hb Bart disappears, and the only abnormality is mild microcytosis. This is a clinically benign condition; therefore, establishing the diagnoses is not necessary in the neonatal period. In people of African extraction, α-thalassemia trait is due to 2 deletions occurring in trans (2 different chromosomes) vs cis deletions (occurring on the same chromosome), which is what is observed in Asians. If an α-thalassemia syndrome is noted in any Asian child, the parents should be referred for α-thalassemia testing and genetic counseling to determine the risk of their future pregnancies being affected by a more severe type of α thalassemia (see further discussion this chapter). The risk of more serious α-thalassemia conditions is not an issue in people of African background unless the mating partner has α-thalassemia trait and is Asian.
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Hemoglobin H disease is due to deletion of 3 α-globin genes (- -/- α). Also, a combination of 2 α-globin deletions and an α-globin gene mutation, most common constant spring (- -/ααcs), results in HbH disease. The clinical features of HbH disease beyond infancy are characterized by mild-to-moderate chronic microcytic anemia with variable degrees of intermittent hemolysis. HbH is unstable and undergoes denaturation in the presence of oxidant stress, thereby forming intracellular inclusions that damage red cells, leading to early removal from circulation. Similar to G-6-PD deficiency, exposure to oxidants can lead to increased hemolysis and worsening anemia. In most cases, HbH disease does not cause clinical problems other than microcytic anemia in neonates. Diagnosis in the neonatal period generally results from newborn screening tests, which detect increased amounts of Hb Bart (usually greater than 20%). Beyond infancy, children with HbH disease have a mild-to-moderate microcytic anemia (Hb 9–10 g/dL), and there can be evidence of hemolysis, such as indirect hyperbilirubinemia and splenomegaly. These infants and children rarely require RBC transfusions.
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Hb Barts hydrops fetalis is due to deletion of all 4 α-globin genes (- -/- -). There are no functional α-globin chains produced; non-α-globin chains accumulate, forming exclusively Hb Bart (γ4) and HbH (β4). Embryos that lack 4 α-globin genes are well until 8 weeks of age, when production of embryonic hemoglobin ceases. Subsequently, due to lack of α-globin chains, Hb Bart becomes the predominant hemoglobin. Hb Bart has a very high oxygen affinity and is unable to efficiently deliver oxygen. Consequently, these fetuses develop anemia and have severe hypoxia, resulting in hydrops with heart failure, generalized edema, and severe growth failure. Most homozygous α-thalassemia fetuses die in utero, although some survive until term due to persistent expression of embryonic globin chains. These hydropic infants often have congenital anomalies and significant neurologic defects. There are case reports of infants with 4 α-globin gene deletions supported with intrauterine transfusions until delivery. Postdelivery, these infants received PRBC transfusions until bone marrow transplantation. This management strategy is controversial as there remain concerns regarding poor in utero neurodevelopment and long-term outcome.
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Besides the fetal effects, there are serious maternal complications in pregnancies of homozygous α thalassemia. Up to 30% of women develop severe preeclampsia. Antepartum hemorrhage, hypertension, renal failure, congestive heart failure, and placental abruption are other known complications. Without proper medical care, up to a 50% mortality rate has been reported.30 Hemoglobin Bart hydrops fetalis can be diagnosed prenatally by DNA-based testing of amniocytes from amniocentesis or chorionic villus sampling. It is important to establish this diagnosis early to avoid the serious maternal complications seen in these pregnancies.
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β-Thalassemia Major: β-Thalassemia major, due to mutations in both β-globin genes, is not a neonatal disease. Anemia from β thalassemia is not notable until 3 months of age when γ-globin production decreases. There are 2 groups of β thalassemia. β0 thalassemia is caused by complete absence of β-chain production; β+ thalassemia has significantly decreased but some β-globin production. Hemoglobin electrophoresis during newborn screening of neonates with β0 thalassemia reveals HbF only, consistent with absent HbA production, while β+-thalassemia patients will have HbF and very small traces of HbA. The diagnosis of β+ thalassemia is therefore only possible after the neonatal period. Infants with β-thalassemia major will become anemic and transfusion dependent by 6–9 months of age. These patients require lifelong transfusions and treatment of iron overload. Bone marrow transplantation is the only curative option.
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Hemoglobin E/β thalassemia is a result of coinheritance of HbE trait and β-thalassemia trait. HbE is a β-globin variant most commonly seen in individuals in India and Southeast Asia, including Thailand, Laos, and Cambodia. There is significant clinical heterogeneity among patients with HbE/β thalassemia, ranging from a mild hemolytic process to a severe chronic transfusion-dependent anemia, identical to that seen with β0-thalassemia major. HbE/β thalassemia is diagnosed by newborn screening hemoglobin electrophoresis, which will demonstrate an FE or FEA pattern. Just like β-thalassemia major, clinical symptoms do not arise until after 3 months of age. However, once the newborn screening tests reveal this hemoglobin disorder, the infant and family should be referred to a hematology treatment center for advice and guidance.
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Sickle Cell Disease: Hemoglobin S is one of the most common β-globin mutations encountered worldwide. The most severe form of sickle cell disease results from inheritance of 2 βs mutations. This genetic pattern results in what is classically known as sickle cell anemia (HbSS disease). Inheritance of one βs mutation and one β-thalassemia trait mutation causes sickle β thalassemia (HbS-β thal), which is identical to sickle cell anemia phenotypically except there is also microcytosis. Coinheritance of βs mutations and βc mutations results in HbS-C disease, which is a milder form of sickle cell disease. All 50 US states have newborn screening programs for sickle cell disease. Hemoglobin patterns are reported in the order of decreasing hemoglobin concentration. The normal neonatal pattern is fetal/adult (FA). Infants with sickle cell anemia and HbS-β thal will have an FS pattern on their newborn screen, while HbS-C disease will provide an FSC pattern. FSA is seen in Hb S-β thal while FAS indicates sickle cell trait.
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Neonates are protected from clinical symptoms of sickle cell disease due to the presence of fetal hemoglobin. However, as HbF concentration decreases after birth, and as HbS production increases, significant complications from cells sickling arise. Newborn screening for sickle cell disease was adopted to ensure early diagnosis to prevent life-threatening complications. Two major complications during infancy are sepsis from encapsulated organisms and splenic sequestration. All neonates with sickle cell anemia should be referred to a sickle cell treatment center for family education and care. Penicillin prophylaxis should begin by 2 months of age, and it is particularly important for sickle cell patients to receive all scheduled vaccines during their first year of life. Sickle cell center staff or primary physicians should provide appropriate education to parents to help them identify splenic sequestration and other sickle cell complications. Couples with a child with sickle cell disease or trait should be referred for further testing and genetic counseling.
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Hypoproliferative Disorders
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Hypoproliferative anemia refers to anemia caused by impaired erythrocyte production (Table 31-2) and is the least-common etiology of anemia in the neonatal period. Lack of specific growth factors stimulating erythropoiesis can lead to hypoproliferative anemia, such as the anemia of prematurity. Decreased erythrocyte progenitors, as seen in isoimmunization with Kell antibodies, can cause decreased red cell production. Abnormalities resulting in increased Epo resistance or abnormalities in Epo receptor expression can result in a decreased red cell mass. Finally, lack of specific substrates or their carriers (such as iron, folate, vitamin B12, or transcobalamin II deficiency) can also lead to deficient production of red cells.
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Congenital/Genetic Hypoproliferative Disorders: Congenital Hypoplastic Anemias
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Congenital hypoplastic anemias refer to a rare group of inherited disorders with impaired RBC production. The most common congenital hypoplastic anemia is Diamond-Blackfan anemia (DBA). Other very rare causes include congenital dyserythropoietic anemia (CDA), and Pearson syndrome.
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Diamond-Blackfan anemia is an AD disorder, estimated at 4–7 cases per million live births, occurring equally in males and females. With the discovery of multiple ribosomal gene mutations and deletions in patients with DBA, it is now firmly established that DBA is a ribosomopathy.32 Mutations in 9 different ribosomal protein genes (RPL 5, RPL 11, RPL 35A, RPS 7, RPS 10, RPS 17, RPS 19, RPS 24, and RPS 26) have been confirmed to be associated with 50% of DBA patients. An additional 20% of patients have deletions of these same ribosomal protein genes, while 30% of patients with DBA remain genetically unclassified.
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In children 6 months of age to toddler years, the main differential diagnosis of RBC aplasia is DBA vs transient erythroblastopenia of childhood (TEC). However, TEC is rarely ever seen in newborns and is unusual in the first 6 months of life. Other causes of red cell aplasia include congenital parvovirus infection, maternal drug exposure, or a marrow infiltrative process such as congenital leukemia. Anemia with reticulocytopenia can also be seen in newborns who have received in utero PRBC transfusions.
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Diamond-Blackfan anemia usually presents in infancy, with approximately 90% of patients diagnosed by 12 months of age. Over 25% of affected infants have severe anemia. Newborns with DBA are otherwise healthy (aside from associated congenital defects) but have severe anemia and reticulocytopenia. DBA is usually an isolated anemia, with other cell lines normal. The anemia is generally macrocytic, but the increased MCV is only appreciated beyond the neonatal period given the large RBC size during the first few months of life. If a bone marrow aspirate is done, it typically reveals normal overall cellularity with a marked decrease in erythroid precursors.
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An important clinical feature of DBA is the presence of congenital anomalies in over 50% of patients. Craniofacial anomalies are most common, but upper limb, hand (particularly thumb), genitourinary, and cardiac anomalies are common. These features can be subtle and may be hard to recognize at birth. The constellation of congenital hypoplastic anemia associated with skeletal anomalies, cleft palate, growth failure, and triphalangial thumbs was previously coined Aase syndrome.33 It is now recognized that this is one of the variants of DBA. Diagnosis of DBA is supported by detecting elevated erythrocyte adenosine deaminase (eADA) activity, found in over 80% of DBA patients.34 Genetic testing for ribosomal protein mutations is available through some commercial gene diagnostic laboratories.
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Packed RBC transfusions are recommended as initial treatment if needed until 1 year of age.35 After this period, steroids are started if the child remains significantly anemic. About 80% of children will respond to steroids, with reticulocytosis noted within 1–2 weeks after initiation of therapy. The natural history of DBA is variable, ranging from a need for chronic red cell transfusions, to a need for continuous administration of small doses of steroids, to spontaneous remission after years of transfusion or steroids. Treatment for those who are steroid refractory or steroid intolerant includes regular PRBC transfusions and iron chelation therapy for preventing and treating iron overload. Hematopoietic stem cell transplantation is the only curative option for DBA, and outcome of matched sibling transplants has been encouraging, with overall survival of greater than 75%. Increasing amounts of data have arisen to support the observation that DBA is a cancer predisposition syndrome. Leukemia and solid tumors have both been reported.36
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Congenital dyserythropoietic anemia is a rare disorder marked by ineffective erythropoiesis, macrocytic or normocytic anemia, and characteristic abnormalities of the nuclear membrane and cytoplasm seen on electron microscopy. Both AD and AR inheritance patterns have been reported. Three types of CDA have been described.37 Type I CDA is characterized by AD inheritance, macrocytic anemia, nuclear chromatin bridges between marrow erythroblasts, and erythroid hyperplasia. Type I CDA has been linked to chromosome 15q15.1–15.3 in a large cohort, and the mutated gene is CDAN1 (codanin-1). Type II, the most common form of CDA, is characterized by normocytic anemia, erythroblastic multinuclearity, and a positive acidified serum test result. A specific mutation in the SEC23B gene on chromosome 20p has been demonstrated in this condition. CDA II appears to result from enzymatic defects in the cellular glycosylation pathway that affects band 3 anion transport activity. Type III CDA is marked by erythroblastic multinuclearity and macrocytosis.
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Congenital dyserythropoietic anemia can present in the newborn period with macrocytic anemia, early jaundice, hepatosplenomegaly, and intrauterine growth retardation. Infants with type I CDA may have bony abnormalities and syndactyly. Fetuses with CDA can present with hydrops fetalis. Although rare, this disorder should be included in the differential diagnosis of newborns with anemia, jaundice, and hepatosplenomegaly. Treatment of this disorder consists of supportive therapy and close observation for side effects of chronic transfusions. Splenectomy may be helpful in some older patients with severe anemia.
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Pearson marrow pancreas syndrome is a disorder involving the hematopoietic system, exocrine pancreas, liver, and kidneys. It presents in infancy with macrocytic anemia, sometimes associated with neutropenia and thrombocytopenia. The bone marrow has normal cellularity but with erythrocyte abnormalities, including vacuolization of erythroid and myeloid precursors and ringed sideroblasts. The disorder is associated with deletions in mitochondrial DNA and appears to involve defects in oxidative phosphorylation. There is no specific therapy. The disorder is usually considered fatal. Some of the few children who survive the hematologic cytopenias later go on to have the clinical and laboratory features associated with Kearns-Sayre syndrome.
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Fanconi anemia is an AR-inherited disorder characterized by marrow failure. In many patients, there are congenital anomalies, including abnormalities in skin pigmentation, gastrointestinal anomalies, renal defects, and upper limb anomalies. In addition, FA is associated with an increased risk of myeloid leukemia and squamous cell cancers, occurring at a relatively younger age than when these tumors usually appear. This disorder is due to a defect in DNA repair, and 13 different FA genes have been identified.38 Peripheral blood lymphocytes are hypersensitive to DNA cross-linking agents such as diepoxybutane (DEB) and mitomycin C, representing a sensitive and specific diagnostic test for FA. The mean age of diagnosis is 6.5 years. The hematologic features of FA are rarely ever present in the newborn period. When FA is identified in neonates, it is because early recognition of congenital abnormalities initially led to specific testing for FA. Definitive treatment of FA necessitates stem cell transplantation, which can ameliorate the hematologic problems, although the increased risk of solid tumors remains.
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Anemia of Prematurity
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In utero, serum Epo concentrations gradually increase through the third trimester and are highest at term. Epo measurements made on neonatal cord blood of laboring and nonlaboring mothers can reflect hypoxic stress during labor and delivery. An increase in NRBCs can be seen with chronic in utero hypoxic stress; however, acute stress (less than 24 hours) may be associated with increased Epo concentrations alone. Serum Epo concentrations at birth normally range from 5 to 100 mU/mL, while Epo concentrations in anemic, nonuremic adults range from 300 to 400 mU/mL.
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In preterm infants, adaptive mechanisms to the extrauterine environment are incomplete, and the transition to term organ function often follows gestational age, regardless of premature delivery. In anemic preterm infants, Epo concentrations are significantly lower than those found in adults, given the degree of their anemia. This normocytic, normochromic anemia is termed the anemia of prematurity. It commonly affects infants 32 weeks’ gestation or less and is the most common anemia seen in the neonatal period.39 The anemia of prematurity is minimally responsive to the addition of iron, folate, vitamin E, or other erythropoietic nutrients. Some infants may be asymptomatic despite hemoglobin concentrations below 8 g/dL, while others demonstrate signs of anemia that appear alleviated by transfusion. Signs associated with the anemia of prematurity include tachycardia, increased episodes of apnea and bradycardia, poor weight gain, tachypnea, an increased oxygen requirement, and elevated serum lactate concentrations that decrease following PRBC transfusion.
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Multiple studies evaluating the use of recombinant Epo to prevent and treat the anemia of prematurity have been published to show that Epo is successful in preterm infants in stimulating erythropoiesis (described in the treatment section of this chapter). Epo recipients will maintain hematocrits 4%–6% greater than placebo recipients (Figure 31-2), total transfusions are decreased, and the number of nontransfused infants are increased.
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Fetal/Neonatal Anemia due to Congenital Infection
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Infections before and after birth can lead to anemia through a hemorrhagic, hemolytic, or hypoproliferative process or a combination of processes. Neonatal sepsis due to Escherichia coli, group B streptococcus, and other perinatal organisms may result in hemolysis, DIC, and hemorrhage. Infants are often jaundiced and have hepatosplenomegaly, although the degree of hyperbilirubinemia does not always correlate with the degree of anemia. Infants may have an elevated direct bilirubin as well, possibly due to infectious involvement with the liver. Bacteria such as E coli will produce hemolytic endotoxins, which result in increased red cell destruction, often associated with a microangiopathic process.
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Fetal and neonatal parvovirus B19 infection can cause severe anemia, hydrops, and fetal demise.40 The infant generally presents with a hypoplastic anemia, but hemolysis can occur as well. The virus replicates in erythroid progenitor cells and shuts down erythropoiesis, resulting in aplastic anemia. In utero transfusions for hydropic fetuses have been investigated but are not successful in all patients. Treatment during aplastic crises with intravenous immunoglobulin (IVIG) leads to resolution of the anemia.
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Both malaria and the human immunodeficiency virus (HIV) can be associated with neonatal anemia. Congenital malaria may occur in major urban areas, where imported cases of malaria are increasing. Congenital HIV infection can be asymptomatic in newborns. Infants born to mothers on zidovudine (AZT) may have hypoplastic anemia due to transplacental side effects of AZT.
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Other Erythropoietin-Responsive Anemias in the Newborn Period
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Late Anemia of Rh Disease. Early anemia in infants with Rh hemolytic disease is caused by ongoing antibody-mediated hemolysis, but a late (age 1 to 3 months) anemia resulting from diminished erythrocyte production can also occur. Late anemia appears to be more common in infants who receive intrauterine transfusions and is characterized by low serum concentrations of Epo but erythroid progenitors that remain highly responsive to recombinant Epo in vitro. Infants with this late anemia will often receive PRBC transfusions until the late anemia resolves, generally by the third or fourth month of life. Following the active hemolytic period when circulating anti-D antibody levels are elevated, the administration of Epo is effective at stimulating erythropoiesis and can serve as an alternative to erythrocyte transfusion.41 Outpatient Epo administration may also diminish or eliminate the need for hospitalization in those centers in which infants are hospitalized for transfusions.
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Kell isoimmunization is a unique hemolytic disorder that selectively impacts marrow erythroid precursors, resulting in both hemolytic and hypoproliferative anemia. Kell positive infants born to Kell-negative mothers can present with severe and protracted anemia.37 Epo administration for neonatal anemia after active hemolysis is resolved can stimulate erythropoiesis.
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Anemia of Bronchopulmonary Dysplasia. Anemia can develop in patients with bronchopulmonary dysplasia (BPD). The anemia of BPD is characterized as normocytic, normochromic, hyporegenerative anemia, with marrow normoblast iron stains that are distinct from those observed in both the anemia of chronic disorders and the anemia of prematurity. Similar to the late anemia of Rh hemolytic disease, the anemia of BPD responds to Epo administration. The explanation for reduced Epo production in patients with BPD requires further study to determine if other factors that could create a relatively Epo-resistant environment are involved, such as interleukin (IL) 1, tumor necrosis factor, and interferon γ.
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Anemia in Neonates Requiring Surgery. Neonates who are born with problems that require surgical repair, such as congenital diaphragmatic hernia, gastroschisis, omphalocele, meningomyelocele, and craniofacial abnormalities often undergo surgery during the period of physiologic anemia. These hospitalized infants undergo blood loss through phlebotomy, the surgery itself, and postoperative care. As a result, the physiologic anemia is exacerbated, and transfusions are often administered to increase hemoglobin concentrations, especially around the time of surgery. These infants respond to Epo administration by increasing erythropoiesis42 and may also benefit from the nonhematopoietic, mitogenic effects of Epo, such as an increase in villous growth.
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In addition to neonates who require surgery, other neonatal populations may benefit from Epo therapy. Epo has been used successfully to treat anemia in newborns with end-stage renal disease due to congenital nephrotic syndrome or polycystic kidney disease and in infants with congenital heart disease awaiting surgery. In addition, infants with hemolytic disease from ABO incompatibility and HS have been treated with Epo.43 Further studies are required in these populations to determine whether treatment with Epo is beneficial and does not cause further harm through increased hemolysis and hyperbilirubinemia.
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The process of blood loss from the intravascular space can be either acute or chronic and can occur at any time during the prenatal, perinatal, or postnatal periods (Table 31-3). Acute hemorrhage generally results in a change in hemoglobin and hematocrit only, while chronic hemorrhage can result in changes to other red cell indices, such as MCV, MCHC, reticulocyte count, and red cell distribution width (RDW).
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Twin-to-twin transfusion syndrome (TTS) is a complication of monochorionic twin gestations and occurs in 5% to 30% of these pregnancies. Depending on the timing and severity of presentation, the perinatal mortality rate can be as high as 70%–100%. In TTS, placental anastomoses allow transfer of blood from one twin to the other. Approximately 70% of monozygous twin pregnancies have monochorionic placentas. Although vascular anastomoses are present in almost all instances of monochorionic placentas, not all anastomoses result in TTS.
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Acute TTS usually results in twins of similar size with hemoglobin concentrations that vary by more than 5 g/dL. Chronic TTS results in the donor twin becoming progressively anemic and growth retarded, while the recipient twin becomes polycythemic, macrosomic, and sometimes hypertensive. The donor twin can become hydropic from profound anemia, while the recipient twin can develop hydrops from congestive heart failure and hypervolemia. The donor twin exists in diminished amniotic fluid volumes, while the recipient twin has increased amniotic fluid due to significant differences in blood volume, renal blood flow, and urine output.
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Chronic TTS can be diagnosed by serial prenatal ultrasounds measuring cardiomegaly, discordant amniotic fluid volume, and fetal growth discrepancy of more than 20%. After birth, the donor twin may be anemic enough to require transfusions and can also experience hypoglycemia, neutropenia, hydrops from severe anemia, growth retardation, and congestive heart failure. The recipient is often the sicker twin, experiencing congestive heart failure associated with hypertrophic cardiomyopathy, hypocalcemia, hypoglycemia, polycythemia, hyperviscosity, and respiratory difficulties. Neurologic evaluation and imaging are important as the risk of antenatally acquired neurologic cerebral lesions is 20% to 30% in both twins. Morbidities include hypoperfusion syndromes from hypotension, multiple cerebral infarctions, and periventricular leukomalacia.44 Long-term neurologic follow-up is necessary and important for all TTS survivors.
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Treatment options vary but should include close monitoring and reduction amniocenteses if needed to decrease uterine stretch and prolong the pregnancy. The average survival rates with serial reduction amniocenteses range from 40% to 70%. Selective fetocide of the hydropic twin has also resulted in the survival of the healthier twin in some studies. Laser surgery to ablate bridging vessels has the best outcomes for TTS pregnancies, resulting in improved survival rates of up to around 50%, with approximately 70% of the pregnancies having at least one survivor. The survival rate without morbidity in the surviving twin is approximately 50%. Meta-analyses have found no differences in outcome between amnioreduction, fetoscopy, septostomy, or close observation for fetuses with TTS.45
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Feto-Maternal Hemorrhage. Maternal and fetal circulating cells may cross the placental barrier at varying times during the pregnancy. The passage of fetal red cells into the maternal circulation is termed feto-maternal hemorrhage (FMH). Approximately 50%–75% of pregnancies are associated with some degree of FMH, usually occurring after the first trimester. Commonly, the volume of fetal blood transferred into the maternal circulation is relatively small, usually on the order of 0.01 to 0.1 mL. About 1 pregnancy in 400 is associated with an FMH of 30 mL or greater, and about 1 pregnancy in 2000 is associated with an FMH of 100 mL or more.46
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In an Rh-incompatible pregnancy, the overall risk of maternal blood group sensitization due to FMH is 16% if the fetus is Rh positive and ABO. The risk decreases to 1.5% if the fetus is Rh positive but ABO incompatible due to the destruction of incompatible cells early during placental transfer. Fetal transfer of cells to the mother occurs during abortions as well: there is a 2% incidence of such transfer with spontaneous abortion and a 4%–5% rate with therapeutic abortion.
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The Kleihauer-Betke stain (KB stain) evaluates the acid elution of hemoglobin from red cells on a sample of maternal blood. Fetal hemoglobin resists acid elution to a greater degree than adult hemoglobin. Maternal cells (in which adult hemoglobin has been eluted from the cell) appear clear (termed ghost cells), while the contaminating fetal cells appear pink.
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KB stains obtained from mothers with increased fetal hemoglobin synthesis, such as mothers with sickle cell disease, thalassemia, or hereditary persistence of fetal hemoglobin, are not reliable; in these cases, other methods should be used to detect FMH, such as flow cytometry using anti-HbF antibodies.47 Diagnosis of a small-volume FMH may be difficult when the mother and infant are ABO incompatible as fetal cells are rapidly cleared from the maternal circulation.
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One in 1000 deliveries is associated with severe (>200 mL) FMH. Severe FMH has been associated with decreased fetal movements and a fetal sinusoidal heart rate (SHR) pattern. Studies noted that decreased/absent fetal movements for a period ranging between 24 hours and 7 days were present for 10%–15% of cases evaluated.48 In this group, two-thirds of the infants either died in utero or during the neonatal period. An SHR pattern was reported in 15% of cases and was associated with decreased fetal movement in 40% of the cases.
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Infants need rapid evaluation and treatment if a significant hemorrhage is suspected. The infant with massive hemorrhage will present with pallor, tachypnea, and delayed capillary refill but may not have a significant oxygen requirement. Hemoglobin concentrations can be extremely low at birth, less than 6 g/dL. Significant metabolic acidosis is often present as a result of poor perfusion.
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Other causes of pallor in the newborn period do exist and should be ruled out once the infant is stable. Infants with asphyxia and infants with chronic hemolytic anemia may also present with pallor (Table 31-4). These diagnoses can be distinguished from acute hemorrhage based on differences in clinical signs (Table 31-5). With chronic hemolytic anemia, clinical signs are mild or absent, and infants respond to conservative therapy with iron alone. Asphyxiated infants will be pale and floppy and may have poor peripheral circulation. The hemoglobin will be stable but may decrease if DIC and subsequent bleeding occur.
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Other causes of prenatal hemorrhage include vaginal bleeding due to placenta previa or abruption, nonelective cesarean section, and deliveries associated with cord compression. Significant FMH has been described following trauma, and fetal hemorrhage into the placenta has been associated with placental chorioangioma.
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Obstetrical complications such as placenta previa, placental abruption, incision or tearing of the placenta during cesarean section, and cord evulsion of normal or abnormal umbilical cords can result in significant neonatal blood loss at the time of delivery. Placental anomalies such as a multilobed placenta and placental chorioangiomas may also be a source of hemorrhage during the perinatal period.
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Placental abruption occurs when there is separation of the placenta from the uterus prior to delivery. Severe fetal growth restriction, prolonged rupture of membranes, chorioamnionitis, hypertension (chronic and pregnancy induced), cigarette smoking, advanced maternal age, and male gender are all risk factors for placental abruption.49 Abruption occurs in approximately 1% of term deliveries, and the incidence of abruption increases with decreasing gestation. Mortality ranges 0.8 to 2 per 1000 births and can be as high as 15% to 20% of the deliveries in which significant abruption occurs. The risk of stillbirth increases significantly when abruption exceeds 50%.
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Women with a history of a previous cesarean birth and increased parity are at increased risk of having a pregnancy complicated by placenta previa,50 a condition in which part or all of the placenta overlies the cervical os. Cigarette smoking increases the risk of placenta previa 2.6- to 4.4-fold. Prenatal diagnosis of vasa previa (anomalous vessels overlying the internal os of the cervix) can be performed with transvaginal color Doppler and should be suspected in any case of antepartum or intrapartum hemorrhage. Although uncommon (1 in 3000 deliveries), the perinatal death rate is high, ranging from 33% to 100% when undetected before delivery.51 Infants are often stillborn.
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Infants born following placental abruption or placenta previa may be anemic and may also present with signs of hypoxia. In these infants, it is important to monitor changes in hematocrit and neurologic signs. The need for postnatal transfusions in the infants is generally associated with the volume of perinatal hemorrhage. The infant’s hemoglobin should be measured at birth and again at 12 to 24 hours whenever there is evidence of placental abruption, placenta previa, or any significant vaginal bleeding. A KB stain can be performed on maternal blood to determine if FMH occurred. Monitoring mothers with a history of second- or third-trimester bleeding with Doppler flow ultrasound to detect placental abnormalities may decrease the incidence of fetal loss and anemia in newborns.
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Cord rupture due to excess traction on a shortened or abnormal umbilical cord usually occurs closer to the fetus than the placenta. Cord aneurysms, varices, and cysts can all lead to a weakened cord. Cord infections, termed funicitis, can also weaken the cord and increase the risk of rupture. In addition, infants born precipitously may be at increased risk for a ruptured cord.
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Hematomas of the cord occur infrequently (1 in 5000–6000 births) but can result in fetal blood loss and may be associated with significant perinatal mortality. Intrauterine fetal demise may occur due to compression of the umbilical vein and arteries by the hematoma. Cord hematomas can result from trauma due to percutaneous umbilical blood sampling (PUBS) and can also be associated with a high maternal α-fetoprotein. Cord hematomas can be accurately diagnosed in utero by ultrasound and differentiated from other lesions of the placenta and cord. The lesion can also result in poor fetal growth and FMH.
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Velamentous insertion of the umbilical cord occurs when the umbilical cord enters the membranes distant from the placenta and is present in approximately 0.5% to 2% of pregnancies. Blood vessels left unprotected by Wharton’s jelly are more vulnerable to tension on the cord, and rupture of anomalous vessels in the absence of traction or trauma can occur even if the cord itself attaches centrally or paracentrally. Fetal mortality is high with velementous insertion, often because detection by routine ultrasound is rare.52
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Blood loss into the placenta, termed fetoplacental hemorrhage, is one of the most common etiologies for a low hematocrit at birth. Of the 120 mL/kg of blood in the fetoplacental unit, approximately one-third remains in the placenta, and blood will continue to flow in the direction of gravity after birth. Fetoplacental hemorrhage occurs when the infant is held above the placenta after birth; for this reason, infants born by cesarean section have smaller blood volumes than those born vaginally.53 In addition, infants can lose 10% to 20% of their total blood volume when born with a tight nuchal cord, which allows blood to be pumped through umbilical arteries toward the placenta while constricting flow through the umbilical vein.
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Blood loss into the subgaleal space is referred to as a subgaleal hemorrhage and can occur during difficult deliveries requiring vacuum or forceps assistance, such as face presentation, occiput posterior presentation, and shoulder dystocia. It is a potentially life-threatening event and must be recognized as early as possible to prevent significant morbidity or mortality. Subgaleal hemorrhage occurs when emissary or “bridging” veins are torn, allowing blood to accumulate in the large potential space between the galea aponeurotica (the epicranial aponeurosis) and the periosteum of the skull (Figure 31-3). The subgaleal space extends from the orbital ridge to the base of the skull and can accommodate an infant’s entire blood volume, or 80 to 90 mL/kg of blood.
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A subgaleal hemorrhage may occur because of preexisting risk factors, such as coagulopathy or asphyxia. The diagnosis should be considered in the presence of a ballotable fluid collection in dependent regions of the infant’s head, coupled with signs of hypovolemia such as tachycardia and metabolic acidosis. A rule of thumb for estimating the volume of blood lost is that every centimeter increase in head circumference represents 38 mL of blood loss. Treatment requires restoration of blood volume and control of bleeding. Exsanguination due to subgaleal hemorrhage has been reported, and the mortality is high if the hemorrhage goes unrecognized.
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Infants undergoing vacuum extraction have an increased risk for subgaleal hemorrhage.54 The duration of vacuum application is thought to be the best predictor of scalp injury, followed by duration of second stage of labor and paramedian cup placement. Of those infants with reported subgaleal hemorrhages, 60%–90% had some history of vacuum or instrument-assisted delivery. A cesarean delivery does not preclude the use of vacuum or forceps, and subgaleal hemorrhage can still occur via this route of delivery. Limiting the frequency and duration of vacuum assistance in high-risk infants may decrease the risk.
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Infants with neonatal alloimmune thrombocytopenia (NAIT) are at increased risk for pre- and postnatal intracranial hemorrhage. NAIT results from platelet-antigen incompatibility between the mother and fetus and occurs in 1 to 2 per 1000 live births. Antibodies to human platelet antigen (HPA) 1a antigen occur most commonly. Of newborns with platelet alloimmunization, 10%–20% will have an intracranial hemorrhage, of which half occur in utero.55 The risk for intracranial hemorrhage is increased in newborns with an affected sibling who had an antenatal intracranial hemorrhage; similar to RhD isoimmunization, the subsequent affected newborns generally have more severe disease than the first sibling. Treatment includes IVIG and platelet transfusions in severe cases.56 Platelets obtained from the mother have a longer half-life because they lack the antigen causing consumption. Treatment of fetal thrombocytopenia includes maternal IVIG administration, maternal steroid administration, and fetal platelet transfusions.
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Anemia appearing after the first 24 hours of life in an unjaundiced infant may result from postnatal hemorrhage. In addition to birth trauma causing visible hemorrhage such as a cephalohematoma, internal hemorrhage to liver, spleen, or other organs can occur. Breech deliveries may be associated with renal, adrenal, or splenic hemorrhage into the retroperitoneal space. Delivery of macrosomic infants, such as infants born to diabetic mothers, may also result in organ damage and hemorrhage.
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The incidence of adrenal hemorrhage is not uncommon, occurring in 1.7 per 1000 births. In addition to causing anemia, adrenal hemorrhage may result in circulatory collapse due to the loss of organ function. Adrenal hemorrhage can also affect surrounding organs. Intestinal obstruction and kidney dysfunction have been reported in infants with adrenal hemorrhage. Diagnosis can be made using ultrasonography, which notes calcifications or cystic masses. Adrenal hemorrhage can be distinguished from renal vein thrombosis (RVT) by ultrasound, in that RVT generally results in a solid mass. Occasionally, both entities may coexist in the same patient. Infants with RVT may have gross or microscopic hematuria and may develop renal failure and hypertension.
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Splenic rupture can result from birth trauma or as a result of distention caused by extramedullary hematopoiesis, such as that seen in erythroblastosis fetalis. Abdominal distension and discoloration, scrotal swelling, and pallor are clinical signs of splenic rupture.
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The newborn liver is prone to iatrogenic rupture, resulting in high morbidity and mortality. Infants may appear asymptomatic until significant hemoperitoneum occurs. Hepatic rupture and hemorrhage occur in both term and preterm infants and have been associated with chest compressions during cardiopulmonary resuscitation. Surgical intervention involving vascular tamponade has been reported to save some infants; however, the mortality remains high.
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Other rare causes of hemorrhage in the newborn include hemangiomas of the gastrointestinal tract, characteristic of Kassaback-Merrit syndrome; vascular malformations of the skin; and hemorrhage into soft tumors, such as giant sacrococcygeal teratomas, thoracic hamartomas, or cystic hygromas. Occult intra-abdominal hemorrhage can occur with fetal ovarian cysts, which are commonly benign and resolve spontaneously.
++
The diagnosis of anemia in the perinatal and postnatal period often requires rapid investigation, laboratory evaluation, and treatment. An immediate assessment of the infant includes determining whether the infant is suffering from acute or chronic anemia, as treatments vary significantly (Table 31-5). Infants presenting in shock from their anemia have most likely suffered massive hemorrhage, and patient stabilization is of utmost importance to avoid organ damage and death. The “ABCs” of newborn resuscitation should be applied: stabilize the infant’s airway, administer oxygen and intubate if necessary, and determine if the infant’s cardiovascular and intravascular volume status is adequate. Immediate volume expansion using normal saline should be performed when a significant acute hemorrhage is suspected. A transfusion of type O, Rh-negative blood (“trauma” blood) may be required in the first hour if massive hemorrhage has occurred. Repeat transfusions of cross-matched PRBCs may be necessary to treat lactic acidosis if oxygen delivery to the tissues is not improved with volume expansion.
++
++
It is helpful to identify the timing of presentation of anemia. Infants with significant acute blood loss before or during delivery may be anemic and hypovolemic at birth, while infants with TTS, chronic FMH, or chronic ongoing hemolysis from isoimmunization may not be immediately symptomatic. Infants with internal trauma and hemorrhage (hepatic, splenic, adrenal, or renal) may not initially be symptomatic but may rapidly decompensate as compensation for intravascular volume loss fails. Attention to details of the infant’s transition period from fetal to postnatal life may be life-saving. As an example, an infant suffering from subgaleal hemorrhage will experience an increased heart and respiratory rate during stage 2 of transition (instead of the expected decrease in heart rate and respiratory rate) due to intravascular volume loss and worsening metabolic acidosis. Close observation during transition will allow rapid diagnosis and potentially life-saving treatment for the infant.
+++
Maternal, Labor, and Delivery History
++
Once the infant is stable, information on maternal, labor, and delivery history can be gathered from both the mother’s and infant’s chart to help determine the cause of anemia. Any family history of anemia, bleeding, “low blood” counts, transfusions, jaundice, or unusual hematologic indices should be identified. Ethnicity of both parents is important to note, as some inherited disorders (eg, G-6-PD deficiency or thalassemia) are more prevalent in specific ethnic groups.
++
Obtaining a thorough labor and delivery history is important, including information on vaginal bleeding, trauma, infection or exposure to infected individuals, and any prescribed or nonprescribed drug use during the pregnancy. The use of cocaine prior to delivery may increase the potential for placental abruption, fetal infarction, and postinfarction hemorrhage. Important maternal laboratory information includes blood type and antibody screen, maternal hepatitis, and syphilis and rubella status.
++
Detailed information regarding labor and delivery can sometimes be difficult to obtain, especially if delivery was not anticipated, such as an emergent cesarean section for loss of fetal heart tones. Episodes of fetal tachycardia or decelerations or other evidence of fetal heart rate abnormalities such as loss of beat-to-beat variability should be noted. The length of labor, vaginal bleeding, evidence of placental abruption, knowledge of placenta previa or vasa previa, and route of delivery should be noted. Information regarding the placenta (cord hematoma, cord rupture, chorioangioma, velementous insertion of the cord) should be gathered and the placenta examined. The use of forceps, vacuum, or other manipulations is important to note. Finally, it is important to identify the presence of multiple gestations, especially those associated with discordant growth.
+++
Laboratory Evaluation
++
Laboratory evaluation of the anemic infant includes a complete blood count including RBC indices and peripheral smear, a reticulocyte count, a direct Coombs test, and total and direct bilirubin. A KB stain of maternal blood can identify fetal cells in the maternal circulation if FMH is suspected. With a thorough history, physical examination, and minimal laboratory evaluation, most causes of anemia in the newborn period can be determined.
++
Treatment of anemia in neonates should be guided by the timing and etiology of the anemia. The management of hemorrhage in the neonatal period depends in part on the etiology of the hemorrhage, its timing, and the extent of hemorrhage. Infants with chronic hemorrhage, such as those with chronic FMH or TTS, may have had time to compensate for a gradual decrease in hemoglobin and may therefore have an adequate intravascular volume despite a low circulating erythrocyte volume (Table 31-5). Those infants will require iron supplementation to replace iron stores depleted by the loss of red cells; however, they are unlikely to require an immediate PRBC transfusion or even volume expansion. Infants experiencing an acute hemorrhage will require volume expansion to improve circulation and organ perfusion.
++
Treatment of anemia due to hemolysis involves understanding the etiology of the hemolysis, the rate of red cell destruction, and the benefits of stimulating neonatal erythropoiesis vs administering an erythrocyte transfusion. Management of hemolytic anemia in neonates will first include managing hyperbilirubinemia. If hemolysis is significant enough and hyperbilirubinemia severe enough to require a double-volume exchange (generally with immune-mediated hemolysis), then correction of hematocrit can occur with the double-volume exchange transfusion. If a double-volume exchange transfusion is not required, acute anemia should be managed with PRBC transfusion. Epo is contraindicated when circulating antibodies directed against the infant’s blood type are still significantly elevated, as stimulating neonatal erythropoiesis may result in increased hemolysis.
++
Treatment of anemia due to hypoproliferative disorders has expanded with the use of erythropoiesis-stimulating agents (ESAs). Most hypoproliferative disorders are associated to a varying degree with low Epo production; thus, treatment with ESAs to increase serum Epo concentrations is often effective.
++
The decision to administer an immediate transfusion of O-negative “trauma” PRBCs should be made carefully, and the emergency use of whole blood prior to type and cross match is generally discouraged. Type O-negative whole blood will contain antibodies directed against A and B blood groups and leukocytes. It should only be used in a hemorrhagic emergency or if the infant’s blood type is known to be O negative.
++
Immediate transfusions will benefit those infants with significant metabolic acidosis and oxygen requirement, generally those with greater than 30%–40% acute blood loss. When considering a transfusion in a preterm infant with a low hematocrit (not associated with an acute drop in hematocrit), the clinician should first determine if the infant needs an immediate increase in oxygen to tissues. If the answer is yes, then treatment consists of a transfusion of PRBCs. If there is no evidence that an immediate increase in oxygen delivery is necessary, then treatment with red cell growth factors and appropriate substrates might be considered. An example of guidelines used to administer transfusions is shown in Table 31-6.
++
++
Treatment of anemic infants with modalities beyond volume expansion, PRBC transfusion, and vitamin and iron supplementation depends on the clinical care offered. The use of recombinant Epo to stimulate erythropoiesis has become more common in neonatal intensive care units; its role in the newborn nursery and in outpatient treatment continues to be refined.
+++
Erythropoiesis-Stimulating Agents
++
The in vitro response of erythroid progenitors from preterm infants led investigators to begin evaluating Epo administration to preterm infants. Since the early 1990s, numerous studies evaluating the use of Epo to prevent and treat the anemia of prematurity have been performed.39 The administration of Epo successfully stimulates erythropoiesis in preterm infants, and transfusion requirements are decreased. Success rates in preventing transfusions in preterm infants are dependent in part on transfusion criteria and the volume of phlebotomy losses. Side effects of Epo in published randomized controlled trials (RCTs) have not differed from placebo, although meta-analyses have suggested an association between early Epo administration and retinopathy of prematurity (ROP). Because a single relevant study was mistakenly categorized in the early Epo analysis instead of the late analysis, this association was incorrectly determined to be statistically significant. This error will be corrected in the next analysis. The development of ROP in preterm infants is likely multifactorial. Moreover, there is evidence in some adult studies of protective effects of Epo in diabetic retinopathy.
++
Darbepoetin alfa (Darbe), a biologically modified version of Epo, was developed by Amgen in 1998. Darbe has a longer serum half-life than Epo in adults and preterm infants, so dosing can be spread over 1 to 2 weeks. Side effects are similar to Epo, and the production of anti-Epo antibodies has not been reported. Studies are under way to evaluate short- and long-term effects of extended courses of Darbe administered to preterm infants. Recent results showed decreased donor and transfusion exposure with weekly Darbe doses of 10 μg/kg.57
++
A minimal number of clinical studies evaluating Darbe administration to preterm infants have been published, and randomized trials are ongoing. In contrast, numerous RCTs evaluating Epo administration to preterm infants have consistently shown evidence of increased erythropoiesis and a decrease in transfusions.
++
A consistent finding in the largest RCTs has been an elevation in hematocrit in the Epo-treated infants compared to those treated with placebo/controls (Figure 31-2). For those neonatal practitioners electing to maintain the hematocrit at higher levels, the use of Epo generally results in an increase of 4%–6% hematocrit points and a decrease in the number of transfusions administered. The increased hematocrit may benefit the infant by increasing available oxygen to tissues and may also provide indirect benefit by avoiding transfusions, which have recently been associated with both necrotizing enterocolitis (NEC) and intraventricular hemorrhage (IVH).58, 59, and 60 Guidelines for Epo and vitamin/iron administration to preterm infants as part of clinical care are presented in Table 31-7.
++
++
Given the risks of transfusion, such as transmission of infectious agents like hepatitis, Trypanosoma cruzi, West Nile virus, and HIV64; the possible development of graft-vs-host disease; and possible associated risks, such as the development of NEC or the worsening of IVH, treatment of anemic neonates using recombinant Epo is an important alternative. Regardless of treatment strategy, a critical understanding of the physiologic influences affecting oxygen availability, delivery, and extraction at the tissue level will best serve clinicians in developing the best evidence-based approach to managing the red cell mass in term and preterm infants.
++
We wish to thank Erin Adair for figure production and Mary Merchant and Cyndie Suniga for their assistance editing the manuscript.
1. +
Jopling
J
et al.. Reference ranges for hematocrit and blood hemoglobin concentration during the neonatal period: data from a multihospital health care system.
Pediatrics. 2009;123(2):e333–e337.
[PubMed: 19171584]
2. +
Ruth
V
et al.. Postnatal changes in serum immunoreactive erythropoietin in relation to hypoxia before and after birth.
J Pediatr. 1990;116(6):950–954.
[PubMed: 2348299]
3. +
Kling
PJ
et al.. Serum erythropoietin levels during infancy: associations with erythropoiesis.
J Pediatr. 1996;128(6):791–796.
[PubMed: 8648538]
5. +
Elalfy
MS, Elbarbary
NS, Abaza
HW. Early intravenous immunoglobin (two-dose regimen) in the management of severe Rh hemolytic disease of newborn—a prospective randomized controlled trial.
Eur J Pediatr. 2011;170(4):461–467.
[PubMed: 20924607]
6. +
Thorp
JM. Utilization of anti-RhD in the emergency department after blunt trauma.
Obstet Gynecol Surv. 2008;63(2):112–115.
[PubMed: 18199384]
7. +
Crowther
C, Middleton
P. Anti-D administration after childbirth for preventing Rhesus alloimmunisation. Cochrane Database Syst Rev. 2000(2):CD000021.
8. +
Wang
M
et al.. Hemolytic disease of the newborn caused by a high titer anti-group B IgG from a group A mother.
Pediatr Blood Cancer. 2005;45(6):861–862.
[PubMed: 16007582]
9. +
Oski
FA. The erythrocyte and its disorders. In: Orkin
SH, Nathan
DG, Ginsberg
D, Look
AT, Fisher
DE, Lux
SE, Hematology of Infancy and Childhood. Philadelphia, PA: Saunders; 2008:21–66.
10. +
Murray
NA, Roberts
IA. Haemolytic disease of the newborn.
Arch Dis Child Fetal Neonatal Ed. 2007;92(2):F83–F88.
[PubMed: 17337672]
11. +
van der Schoot
CE
et al.. Prenatal typing of Rh and Kell blood group system antigens: the edge of a watershed.
Transfus Med Rev. 2003;17(1):31–44.
[PubMed: 12522770]
12. +
Vaughan
JI
et al.. Inhibition of erythroid progenitor cells by anti-Kell antibodies in fetal alloimmune anemia.
N Engl J Med. 1998;338(12):798–803.
[PubMed: 9504940]
14. +
Kaplan
M, Hammerman
C. Glucose-6-phosphate dehydrogenase deficiency: a hidden risk for kernicterus.
Semin Perinatol. 2004;28(5):356–364.
[PubMed: 15686267]
15. +
Watchko
JF. Identification of neonates at risk for hazardous hyperbilirubinemia: emerging clinical insights.
Pediatr Clin North Am. 2009;56(3):671–687, table of contents.
[PubMed: 19501698]
16. +
Kaplan
M, Hammerman
C. Severe neonatal hyperbilirubinemia. A potential complication of glucose-6-phosphate dehydrogenase deficiency.
Clin Perinatol. 1998;25(3):575–590, viii.
[PubMed: 9779335]
17. +
Kaplan
M
et al.. Gilbert syndrome and glucose-6-phosphate dehydrogenase deficiency: a dose-dependent genetic interaction crucial to neonatal hyperbilirubinemia.
Proc Natl Acad Sci U S A. 1997;94(22):12128–12132.
[PubMed: 9342374]
18. +
Johnson
L
et al.. Clinical report from the pilot USA Kernicterus Registry (1992 to 2004).
J Perinatol. 2009;29(Suppl 1):S25–S45.
[PubMed: 19177057]
19. +
Bhutani
VK, Stark
AR, Lazzeroni
LC
et al.. Predischarge screening for severe neonatal hyperbilirubinemia identifies infants who need phototherapy.
J Pediatr. 2013;162(3):477–482.
[PubMed: 23043681]
20. +
Zanella
A
et al.. Red cell pyruvate kinase deficiency: molecular and clinical aspects.
Br J Haematol. 2005;130(1):11–25.
[PubMed: 15982340]
21. +
Christensen
RD, Eggert
LD, Baer
VL, Smith
KN. Pyruvate kinase deficiency as a cause of extreme hyperbilirubinemia in neonates from a polygamist community.
J Perinatol. 2010;30(3):233–236.
[PubMed: 20182430]
22. +
Zanella
A
et al.. Pyruvate kinase deficiency: the genotype-phenotype association.
Blood Rev. 2007;21(4):217–231.
[PubMed: 17360088]
23. +
Glader
B Hereditary hemolytic anemias due to red blood cell enzyme disorders. In: Greer
JP
et al., eds. Wintrobe’s Clinical Hematology. Philadelphia, PA: Lippincott, Williams & Wilkins; 2009:933–955.
24. +
Steiner
LA, Gallagher
PG. Erythrocyte disorders in the perinatal period.
Semin Perinatol. 2007;31(4):254–261.
[PubMed: 17825683]
25. +
Gallagher
PG. Update on the clinical spectrum and genetics of red blood cell membrane disorders.
Curr Hematol Rep. 2004;3(2):85–91.
[PubMed: 14965483]
26. +
Stamey
CC, Diamond
LK. Congenital hemolytic anemia in the newborn; relationship to kernicterus.
AMA J Dis Child. 1957;94(6):616–622.
[PubMed: 13478296]
27. +
Gallagher
PG. Hereditary elliptocytosis: spectrin and protein 4.1R.
Semin Hematol. 2004;41(2):142–164.
[PubMed: 15071791]
28. +
Delaunay
J, Stewart
G, Iolascon
A. Hereditary dehydrated and overhydrated stomatocytosis: recent advances.
Curr Opin Hematol. 1999;6(2):110–114.
[PubMed: 10088641]
29. +
Stewart
GW
et al.. Thrombo-embolic disease after splenectomy for hereditary stomatocytosis.
Br J Haematol. 1996;93(2):303–310.
[PubMed: 8639421]
30. +
Vichinsky
EP. Alpha thalassemia major—new mutations, intrauterine management, and outcomes. Hematology Am Soc Hematol Educ Program. 2009:35–41.
31. +
Hoppe
CC. Newborn screening for non-sickling hemoglobinopathies. Hematology Am Soc Hematol Educ Program. 2009:19–25.
32. +
Clinton
C, Gazda
HT. Diamond-Blackfan anemia. In: Pagon
RA
et al., eds. GeneReviews. Seattle, WA; 1993.
33. +
Aase
JM, Smith
DW. Congenital anemia and triphalangeal thumbs: a new syndrome.
J Pediatr. 1969;74(3):471–474.
[PubMed: 5764780]
34. +
Fargo
JH
et al.. Erythrocyte
adenosine deaminase: diagnostic value for Diamond-Blackfan anaemia.
Br J Haematol. 2013;160(4):547–554.
[PubMed: 23252420]
35. +
Vlachos
A
et al.. Diagnosing and treating Diamond Blackfan anaemia: results of an international clinical consensus conference.
Br J Haematol. 2008;142(6):859–876.
[PubMed: 18671700]
36. +
Vlachos
A
et al.. Incidence of neoplasia in Diamond Blackfan anemia: a report from the Diamond Blackfan Anemia Registry.
Blood. 2012;119(16):3815–3819.
[PubMed: 22362038]
37. +
Iolascon
A, Russo
R, Delaunay
J. Congenital dyserythropoietic anemias.
Curr Opin Hematol. 2011;18(3):146–151.
[PubMed: 21378561]
38. +
Shimamura
A, Alter
BP. Pathophysiology and management of inherited bone marrow failure syndromes.
Blood Rev. 2010;24(3):101–122.
[PubMed: 20417588]
39. +
Bishara
N, Ohls
RK. Current controversies in the management of the anemia of prematurity.
Semin Perinatol. 2009;33(1):29–34.
[PubMed: 19167579]
40. +
Chauvet
A
et al.. Ultrasound diagnosis, management and prognosis in a consecutive series of 27 cases of fetal hydrops following maternal parvovirus B19 infection.
Fetal Diagn Ther. 2011;30(1):41–47.
[PubMed: 21502743]
41. +
Ohls
RK, Wirkus
PE, Christensen
RD. Recombinant erythropoietin as treatment for the late hyporegenerative anemia of Rh hemolytic disease.
Pediatrics. 1992;90(5):678–680.
[PubMed: 1408538]
42. +
Bierer
R
et al.. Erythropoietin increases reticulocyte counts and maintains hematocrit in neonates requiring surgery.
J Pediatr Surg. 2009;44(8):1540–1545.
[PubMed: 19635302]
43. +
Hosono
S
et al.. Successful recombinant erythropoietin therapy for a developing anemic newborn with hereditary spherocytosis.
Pediatr Int. 2006;48(2):178–180.
[PubMed: 16635181]
44. +
Lopriore
E, Oepkes
D, Walther
FJ. Neonatal morbidity in twin-twin transfusion syndrome.
Early Hum Dev. 2011;87(9):595–599.
[PubMed: 21784588]
45. +
Salomon
LJ
et al.. Long-term developmental follow-up of infants who participated in a randomized clinical trial of amniocentesis vs laser photocoagulation for the treatment of twin-to-twin transfusion syndrome. Am J Obstet Gynecol. 2010;203(5):444.e1–7.
46. +
Wylie
BJ, D’Alton
ME. Fetomaternal hemorrhage.
Obstet Gynecol. 2010;115(5):1039–1051.
[PubMed: 20410781]
47. +
Chambers
E
et al.. Comparison of haemoglobin F detection by the acid elution test, flow cytometry and high-performance liquid chromatography in maternal blood samples analysed for fetomaternal haemorrhage.
Transfus Med. 2012; 22(3):199–204.
CrossRef
[PubMed: 22429383]
48. +
Wilcock
FM, Kadir
RA. Fetomaternal haemorrhage—a cause for unexplained neonatal death, presenting with reduced fetal movements and non-reactive fetal heart trace.
J Obstet Gynaecol. 2004;24(4):456–457.
CrossRef
[PubMed: 15203594]
49. +
Tikkanen
M. Placental abruption: epidemiology, risk factors and consequences.
Acta Obstet Gynecol Scand. 2011;90(2):140–149.
CrossRef
[PubMed: 21241259]
50. +
Fishman
SG, Chasen
ST, Maheshwari
B. Risk factors for preterm delivery with placenta previa.
J Perinat Med. 2011;40(1):39–42.
[PubMed: 22085154]
51. +
Rosenberg
T
et al.. Critical analysis of risk factors and outcome of placenta previa.
Arch Gynecol Obstet. 2011;284(1):47–51.
CrossRef
[PubMed: 20652281]
52. +
Rao
KP
et al.. Abnormal placentation: evidence-based diagnosis and management of placenta previa, placenta accreta, and vasa previa.
Obstet Gynecol Surv. 2012;67(8):503–519.
CrossRef
[PubMed: 22926275]
53. +
Garofalo
M, Abenhaim
HA. Early versus delayed cord clamping in term and preterm births: a review.
J Obstet Gynaecol Can. 2012;34(6):525–531.
[PubMed: 22673168]
54. +
Chang
HY
et al.. Neonatal subgaleal hemorrhage: clinical presentation, treatment, and predictors of poor prognosis.
Pediatr Int. 2007;49(6):903–907.
CrossRef
[PubMed: 18045294]
55. +
McQuilten
ZK
et al.. A review of pathophysiology and current treatment for neonatal alloimmune thrombocytopenia (NAIT) and introducing the Australian NAIT registry.
Aust N Z J Obstet Gynaecol. 2011;51(3):191–198.
CrossRef
[PubMed: 21631435]
56. +
Symington
A, Paes
B. Fetal and neonatal alloimmune thrombocytopenia: harvesting the evidence to develop a clinical approach to management.
Am J Perinatol. 2011;28(2):137–144.
CrossRef
[PubMed: 20700860]
57. +
Ohls
RK, Christensen
RD, Kamath-Rayne
BD
et al.. A randomized, masked, placebo-controlled study of darbepoetin alfa in preterm infants.
Pediatrics. 2013;132:1–9.
CrossRef
[PubMed: 23796740]
58. +
Christensen
RD. Association between red blood cell transfusions and necrotizing enterocolitis.
J Pediatr. 2011;158(3):349–350.
CrossRef
[PubMed: 21146187]
59. +
Baer
VL
et al.. Red blood cell transfusion of preterm neonates with a grade 1 intraventricular hemorrhage is associated with extension to a grade 3 or 4 hemorrhage.
Transfusion. 2011;51(9):1933–1939.
CrossRef
[PubMed: 21382049]
60. +
Christensen
RD
et al.. Postponing or eliminating red blood cell transfusions of very low birth weight neonates by obtaining all baseline laboratory blood tests from otherwise discarded fetal blood in the placenta.
Transfusion. 2011;51(2):253–258.
CrossRef
[PubMed: 20723166]
61. +
Donato
H, Vain
N, Rendo
P
et al.. Effect of early versus late administration of human recombinant erythropoietin on transfusion requirements in premature infants: results of a randomized, placebo-controlled, multicenter trial.
Pediatrics. 2000;105:1066–1072.
CrossRef
[PubMed: 10790464]
62. +
Ohls
RK, Ehrenkranz
RA, Wright
LL
et al.. Effects of early erythropoietin therapy on the transfusion requirements of preterm infants below 1250 grams birth weight: a multicenter, randomized, controlled trial.
Pediatrics. 2001;108:934–942.
CrossRef
[PubMed: 11581447]
63. +
Haiden
N, Schwindt
J, Cardona
F
et al.. Effects of a combined therapy of erythropoietin, iron, folate, and vitamin B12 on the transfusion requirements of extremely low birth weight infants.
Pediatrics. 2006;118:2004–2013.
CrossRef
[PubMed: 17079573]
64. +
Kleinman
S
et al.. The National Heart, Lung, and Blood Institute retrovirus epidemiology donor studies (Retrovirus Epidemiology Donor Study and Retrovirus Epidemiology Donor Study-II): twenty years of research to advance blood product safety and availability.
Transfus Med Rev. 2012;26(4):281–304, 304.e1–2.
CrossRef
[PubMed: 22633182]