Alpha Thalassaemia in American Blacks: a Study of a Family with Five Cases of Haemoglobin H Disease

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Abstract
Five cases of HbH disease were discovered in a large family of American Blacks. Anemia was mild with PCV [packed cell volume] ranging from 0.275-0.405. The amount of HbH was 2-6%. Studies of Hb synthesis in peripheral blood reticulocytes demonstrated marked deficits in .alpha. globin production with an average .alpha./.beta. ratio of 0.31 (range 0.22-0.36). Additional family members (18) had evidence of thalassemia trait and were provisionally classified as .alpha.-thal-1 (average MCV [mean corpuscular volume] 65.2 f[femto]l; range 59-70) or .alpha.-thal-2 (average MCV 79.6 fl; range 74-88). A subject with .alpha.-thal-1 trait had an .alpha./.beta. ratio of 0.56; the average for 5 cases of .alpha.-thal-2 was 0.73. One other family member was thought to be homozygous for .alpha.-thal-2 trait and exhibited an MCV of 65 fl with an .alpha./.beta. ratio of 0.5. In Blacks with .alpha. thalassemia the proportion of HbH is lower and the severity of anemia is less than in certain other racial groups, e.g. Southeast Asians. The degree of hypochromia and microcytosis and the imbalance in .alpha. and .beta. globin synthesis appear to be similar in Blacks and other races. The milder clinical course of HbH disease in Blacks apparently is not a result of greater .alpha. globin production in that population of thalassemics.