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## Alpha Thalassemia ### Silent Carrier State - Deletion of one alpha gene, leaving three functional alpha genes - Usually no hematologic abnormalities are present. However, borderline low MCV (78-80fL) may be seen - No reliable way to diagnose silent carriers by hematologic methods; Must be done...

## Alpha Thalassemia ### Silent Carrier State - Deletion of one alpha gene, leaving three functional alpha genes - Usually no hematologic abnormalities are present. However, borderline low MCV (78-80fL) may be seen - No reliable way to diagnose silent carriers by hematologic methods; Must be done by genetic mapping. ### Alpha Thalassemia Trait (Alpha Thalassemia Minor) - Caused by two missing alpha genes. May be homozygous (-a/-a: Alpha +) or heterozygous (--/aa; Alpha 0). - Shows mild microcytic, hypochromic anemia. - MCV between 70-75 fL. - Should be differentiated from iron deficiency anemia. ### Hemoglobin H Disease - Second most severe form of alpha thalassemia. - Usually caused by presence of only one gene producing alpha chains (--/-a). - Results in accumulation of excess unpaired gamma or beta chains. - Born with 10-40% Bart's hemoglobin (y4), gradually replaced with hemoglobin H (β4). - In adult, have about 10-20% Hb H. - The patient has moderate anemia however, infections, pregnancy, exposure to oxidative drugs may trigger hemolytic crisis. - RBCs are microcytic, hypochromic with marked poikilocytosis, and numerous target cells. - Hb H is vulnerable to oxidation. Gradually precipitates in vivo to form inclusions of denatured hemoglobin. Cells been described as having "golf ball" appearance when stained with brilliant cresyl blue. ### Bart's Hydrops Fetalis Syndrome/ alpha (0) thalassemia - Most severe form. Incompatible with life. - Have no functioning alpha chain genes - Baby born with hydrops fetalis (edema and ascites). Also, hepatosplenomegaly and cardiomegaly are present. - Predominant hemoglobin is Hb Barts (4 gamma chains) with traces ofHb H (4 beta chains). - Hemoglobin Bart's has high oxygen affinity so cannot carry oxygen to tissues. - Fetus dies in utero or shortly after birth. - There is severe hypochromic, microcytic anemia with numerous NRBCs. ### Alpha Thalassemia with Hb S - Alpha thalassemia can occur in combination with hemoglobin S. Is fairly common combination in populations of African origin. ### Blood Picture #### In carrier state (thalassemia minor) - Mild anemia or no anemia - Low MCV and MCH - Normal or near normal RBC count - RBC count is typically normal - Elevated RBC count when compared to iron deficiency #### In thalassemia major - Moderate to marked anemia - Low MCV and MCH - High RDW - Decreased RBC count - PB stained smear shows: - Microcytic, hypochromic red blood cells. - Moderate to severe poikilocytosis - Many target cells - Polychromasia