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Key Features

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  • Predominately African, Mediterranean, Middle Eastern, Chinese, or Southeast Asian ancestry

  • Microcytic, hypochromic anemia of variable severity

  • Generally Bart's hemoglobin detected by neonatal screening

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Clinical Findings

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  • Depend on the number of α-globin genes deleted

  • Persons with three α-globin genes (one-gene deletion) are asymptomatic

  • Persons with two α-globin genes (two-gene deletion) are typically asymptomatic

  • Persons with one α-globin gene (three-gene deletion)

    • Have a mild to moderately severe microcytic hemolytic anemia (hemoglobin level of 7–10 g/dL)

    • May be accompanied by hepatosplenomegaly and some bony abnormalities caused by the expanded medullary space

  • Deletion of all four α-globin genes

    • Causes severe intrauterine anemia

    • Results in hydrops fetalis and fetal demise or neonatal death shortly after delivery

    • Extreme pallor and massive hepatosplenomegaly are present

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Diagnosis

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  • Persons with three α-globin genes (one-gene deletion): no hematologic abnormalities

  • Hemoglobin electrophoresis

    • In the neonatal period shows 0–3% Bart's hemoglobin, which is a variant hemoglobin composed of four γ-globin chains

    • Normal after the first few months of life

  • Persons with two α-globin genes (two-gene deletion)

    • Mean corpuscular volume (MCV) is usually less than 100 fL at birth

    • Hematologic studies in older infants and children show a normal or slightly decreased hemoglobin level with a low MCV and a slightly hypochromic blood smear with some target cells

  • Persons with one α-globin gene (three-gene deletion)

    • Reticulocyte count is elevated

    • Red cells show marked hypochromia and microcytosis with significant poikilocytosis and some basophilic stippling

    • Incubation of red cells with brilliant cresyl blue (hemoglobin H preparation) shows inclusion bodies formed by denatured hemoglobin H

  • Deletion of all four α-globin genes

    • Hemoglobin electrophoresis reveals a predominance of Bart's hemoglobin with a complete absence of normal fetal or adult hemoglobin

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Treatment

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  • Persons with α-thalassemia trait require no treatment

  • Those with hemoglobin H disease should receive supplemental folic acid and avoid the same oxidant drugs that cause hemolysis in persons with G6PD deficiency because exposure to these drugs may exacerbate their anemia

  • Anemia may also be exacerbated during periods of infection, and transfusions may be required

  • Hypersplenism may develop later in childhood and require surgical splenectomy

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