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Anemia may be the first recognized hematologic finding in a child whose bone marrow is not functioning normally. It may be the sole problem (single cytopenia) or occur in conjunction with deficits in other cell lineages (pancytopenia). The cause may be a deficiency of a required nutrient (iron, folic acid, vitamin B12), the inability of the marrow to use nutrients because of concomitant medical conditions (inflammation, hypothyroidism), or intrinsic bone marrow failure. Bone marrow failure may be either inherited or acquired (aplastic anemia). These anemias are due to diminished RBC production.

Nutritional Anemias

In pediatric patients, the most common nutritional anemia is due to iron deficiency, which is discussed in Chapter 431. Anemias due to decreased production are generally macrocytic with an increased mean cell volume (MCV) and mean cell hemoglobin (MCH). Although diagnosed far more often in adults than children, most commonly, nutritional anemias are due to a dietary deficiency of folic acid, cobalamin (vitamin B12), or both.

Laboratory Findings

In both, the hemoglobin concentration is decreased, reticulocyte count is inappropriately low for the degree of anemia, and mean cell volume (MCV) and mean cell hemoglobin (MCH) are increased. The blood smear shows macroovalocytes, anisocytosis, and poikilocytosis. Neutrophils have hypersegmented nuclei. WBC and platelet counts are usually within the normal range, but may decrease with more severe deficits. The bone marrow shows ineffective erythropoiesis with erythroid hyperplasia and delayed maturation of the nuclei compared to the cytoplasm.

Folic Acid Deficiency

Folic acid deficiency is rare in infants and children in North America due to the routine supplementation of commercial infant formulas and flour-containing products such as bread and pasta. Classically, it occurs with severe malnutrition and in infants fed unpasteurized goat’s milk. As folic acid is absorbed in the jejunum, malabsorption may occur with celiac disease or due to the inhibitory effects of anticonvulsants such as Phenobarbital and phenytoin. Cytotoxic medications, such as methotrexate, achieve their therapeutic benefit by alteration of folic acid metabolism (see Chapter 517). Deficiency may also occur in persons with increased folate requirements such as in chronic hemolytic anemia. Folic acid–deficient hematopoiesis is best diagnosed by measurement of RBC, not serum, folate levels. Folate deficiency is treated with oral medication.

Cobalamin or Vitamin B12 Deficiency

This is also relatively uncommon in children, occurring most often in breast-fed infants of mothers who are either strict vegetarians or who themselves have pernicious anemia (due to antibodies against intrinsic factor, which is required for absorption of vitamin B12). Absorption of cobalamin occurs in the terminal ileum, so deficiency may develop from impaired absorption that occurs in Crohn disease, pancreatitis, bacterial overgrowth, and surgical resection of the terminal ileum. Inborn errors of metabolism (transcobalamin II deficiency or methylmalonic aciduria), and rarely lack of intrinsic factor, may also lead to ...

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