α-thalassemia

Individuals with α-thalassemia have an excess of beta globin chain due to impaired production of alpha globin chains. There are four commonly recognized alpha thalassemia disorders and these are described in the following table:

DISORDER TYPE
PHENOTYPE DIAGNOSES MANAGEMENT
α-thalassemia-2 trait, referred to as “silent carrier” or alpha thalassemia minima Individuals do not usually exhibit symptoms and generally have normal routine blood findings Can be unreliable; only diagnosed by DNA analysis Will depend on symptoms;

usually no specific therapy

DISORDER TYPE
PHENOTYPE DIAGNOSES MANAGEMENT
α-thalassemia-1 trait, also called α-thalassemia minor; occurs due to the loss of two of the four globin genes;

resembles mild βeta thalassemia trait

Adults may have mild anemia; red cells are small (microcytic) and their hemoglobin electrophoresis pattern is normal Peripheral blood smear shows hypochromia, microcytosis, and target cells;

pregnant women from an ethnic background at-risk for thalassemia should be screened by both CBC and a hemoglobin electrophoresis and if necessary progress to DNA studies

No specific therapy;

requires careful genetic counseling

DISORDER TYPE
PHENOTYPE DIAGNOSES MANAGEMENT
Hemoglobin H is composed of four beta chains Common symptoms are: chronic hemolysis (breaking down of red blood cells), enlargement of both liver and spleen (hepatosplenomegaly), premature biliary tract disease, and iron overload Peripheral blood smear, bone marrow examination;

in California, Universal Newborn Screening for Hb H and Hb H-Constant Spring is performed on all newborns; prenatal testing and genetic counseling is required for precise diagnosis

Close monitoring of the blood count and possible transfusional intervention may be required during periods of infection or exposure to certain drugs
DISORDER TYPE
PHENOTYPE DIAGNOSES MANAGEMENT
Hydrops fetalis with Hb Barts is due to the loss of all four alpha globins This condition is incompatible with life outside the uterus;

infants usually die within a few hours after birth, unless supported with massive total exchange transfusions either before birth or immediately after

Symptoms occur usually in utero (pregnancy in the uterus);

prenatal testing and genetic counseling is required for precise diagnosis

If survives the neonatal period because of medical intervention then treated in the same way as β-thalassemia major

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