alpha-thalassemia
noun
al·pha-thal·as·se·mia
variants:
also α-thalassemia \ ˌal-fə-ˌtha-lə-ˈsē-mē-ə 
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Medical Definition of alpha-thalassemia
: thalassemia in which the hemoglobin chains designated alpha are affected
Note: The severity of alpha-thalassemia is directly related to the number of defects occurring in the four genes controlling synthesis of the alpha hemoglobin chain. Defects in one or two of the genes causes a condition that is asymptomatic or marked by mild anemia. Defects in three of the genes cause a condition marked by hemolytic anemia and enlargement of the spleen. Defects in all four genes is fatal and results in a fetus that is stillborn or critically ill with hydrops fetalis.
— compare beta-thalassemia