beta-thalassemia

thalassemia /thal·as·se·mia/ (thal″ah-se´me-ah) a heterogeneous group of hereditary hemolytic anemias marked by a decreased rate of synthesis of one or more hemoglobin polypeptide chains, classified according to the chain involved (α, β, δ); the two major categories are α- and β-thalassemia.

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α-thalassemia  that caused by diminished synthesis of alpha chains of hemoglobin. The homozygous form is incompatible with life, the stillborn infant displaying severe hydrops fetalis. The heterozygous form may be asymptomatic or marked by mild anemia.

β-thalassemia  that caused by diminished synthesis of beta chains of hemoglobin. The homozygous form is called t. major and the heterozygous form is called t. minor.

thalassemia ma´jor  the homozygous form of β, in which hemoglobin A is completely absent; it appears in the newborn period and is marked by hemolytic, hypochromic, microcytic anemia, hepatosplenomegaly, skeletal deformation, mongoloid facies, and cardiac enlargement.

thalassemia mi´nor  the heterozygous form of β, usually asymptomatic, although there is sometimes mild anemia.

sickle cell–thalassemia  a hereditary anemia involving simultaneous heterozygosity for hemoglobin S and thalassemia.

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beta-thalassemia,

an anemia that is caused by diminished synthesis of beta chains of hemoglobin. The homozygous form is known as thalassemia major and the heterozygous form is known as thalassemia minor. See thalassemia.

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beta-thalassemia (bāˑ·t-tha·ls·sēˑ·mē·),

n type of anemia occurring as a result of reduced synthesis of the beta chains of hemoglobin.