515 HOMOZYGOUS β-THALASSEMIA WITH HIGH LEVEL OF Hb A₂

Abstract

A 15 y o Black male with severe anemia, splenomegaly and typical thalassemic blood picture had 12.4% Hb A₂. Family studies (table) were consistent with homozygosity for the β-thal.

gene. The α/non-α globin synthesis ratio of the father's reticulocytes revealed the presence of α-thal. Analysis of the proband's A₂ Hb showed asparagine at δ Tp 2 and one methionine residue at δ Tp 13 suggesting a normal δ chain structure. The α/non-α ratio and % Hb F in the proband were lower than usual for homozygous β-thal. These values and the marked increase in Hb A₂ are probably due to the ameliorating effect of an associated α-thal. gene rather than to the presence of a Miyada-like hemoglobin, as has been postulated for a similar kindred (Biochem. Genet.: 10, 135, 1973).

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