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Key Features

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Essentials of Diagnosis
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  • Neonatal screening test usually with hemoglobins FS, FSC, or FSA (S > A)

  • Predominantly African, Mediterranean, Middle Eastern, Indian, or Caribbean ancestry

  • Anemia, elevated reticulocyte count, usually jaundice

  • Recurrent episodes of musculoskeletal or abdominal pain

  • Often hepatomegaly and splenomegaly that resolves

  • Increased risk of bacterial sepsis

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General Considerations
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  • Sickle cell disease encompasses a family of disorders with manifestations secondary to the propensity of deoxygenated sickle hemoglobin (S) to polymerize

  • Polymerization of sickle hemoglobin

    • Distorts erythrocyte morphology

    • Decreases red cell deformability

    • Causes a marked reduction in red cell life span

    • Increases blood viscosity

    • Predisposes to inflammation, coagulation activation, and episodes of vaso-occlusion

  • Sickle cell anemia

    • Most severe sickling disorder

    • Caused by homozygosity for the sickle gene

    • Most common form of sickle cell disease

  • Other clinically important sickling disorders are compound heterozygous conditions in which the sickle gene interacts with genes for hemoglobins C, DPunjab, OArab, CHarlem, or β-thalassemia

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Demographics
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  • Overall, occurs in about 1 of every 400 African-American infants

  • Eight percent of African Americans are heterozygous carriers of the sickle gene and thus have sickle cell trait

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Clinical Findings

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  • Physical findings are normal at birth

  • Symptoms are unusual before age 3–4 months because high levels of fetal hemoglobin inhibit sickling

  • Moderately severe hemolytic anemia

    • May be present by age 1 year

    • Causes pallor, fatigue, and jaundice

    • Predisposes to the development of gallstones during childhood and adolescence

  • Intense congestion of the spleen with sickled cells may cause splenomegaly in early childhood

    • Results in functional asplenia as early as age 3 months in sickle cell anemia

    • Places children at great risk for overwhelming infection with encapsulated bacteria, particularly pneumococci

  • Acute splenic sequestration characterized by

    • Sudden enlargement of the spleen with pooling of red cells

    • Acute exacerbation of anemia

    • Shock and death (in severe cases)

  • Dactylitis occurs in up to 50% of children with sickle cell anemia before age 3 years

  • Recurrent episodes of abdominal and musculoskeletal pain may occur throughout life

  • Overt strokes occur in about 11% of children with sickle cell anemia and tend to be recurrent

  • Acute chest syndrome

    • Characterized by fever, pleuritic chest pain, and acute pulmonary infiltrates with hypoxemia

    • Caused by pulmonary infection, infarction, or fat embolism from ischemic bone marrow

  • All tissues are susceptible to damage from vaso-occlusion, and multiple organ dysfunction is common by adulthood in those with sickle cell anemia or sickle β0-thalassemia

  • Manifestations generally develop less frequently in those with SC and S β+-thalassemia

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Diagnosis

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  • Baseline hemoglobin level of 7–10 g/dL

    • Seen in children with sickle cell anemia

    • May fall to life-threatening levels at the time of a splenic sequestration or aplastic crisis

    • Often occurs in association with parvovirus B19 infection

  • Baseline reticulocyte count is elevated markedly

  • Anemia is usually normocytic or ...

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