thalassemia major

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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thalassemia ma·jor (mjr)

n.

A usually fatal form of thalassemia appearing in infancy or childhood in which normal hemoglobin is absent, characterized by severe anemia, enlargement of the heart, liver, and spleen, and skeletal deformation. Also called Cooley's anemia.

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thalamus (thal´mus),

n an ovoid mass in the brain immediately lateral to the third ventricle that serves as the principal relay and integration station for the sensory systems in the body.

thalassemia

n a hereditary, chronic, hemolytic anemia with erythroblastosis. A complex of hereditary disorders characterized by microcytosis and increased red blood cell destruction and often associated with abnormal hemoglobins and increased normal trace hemoglobins. These disorders are prevalent in people of Mediterranean, African, and Asian ancestry. Disorders include Cooley's anemia, Cooley's trait, hemoglobin H disease, Hb S-thalassemia, Hb Cthalassemia, and Hb E-thalassemia.

thalassemia major (Cooley's anemia, erythroblastic anemia, famil-ial erythroblastic anemia, hereditary microcytosis, Mediterranean anemia, Mediterranean disease),

n the severe homozygous form of thalassemia characterized by a marked microcytic hypochromic anemia, atypical nucleated red blood cells, marked increase in hemoglobin F, and skeletal changes (underdevelopment, mongoloid facies, anterior open bite).

thalassemia minor (Cooley's trait),

n a heterozygous form of thalassemia that is a carried state with relatively mild manifestations; α₂ hemoglobin is elevated.