Hb Q(India) and its interaction with beta-thalassaemia: a study of 64 cases from India.

Haemoglobin Q (Hb Q), a relatively uncommon alpha-chain structural Hb variant, has been reported either in the heterozygous state or interacting with beta-thalassaemia. Individuals inheriting Hb Q generally are asymptomatic and are diagnosed by chance during population screening or as a part of a family study. This paper represents the first large study from India of 64 cases of Hb Q, documenting the haematological and molecular findings on 36 cases of Hb Q trait, 22 of Hb Q beta-thalassaemia trait and three of Hb Q beta-thalassaemia major, as well as a family of Hb Q homozygous cases. Hb Q is detected by Hb electrophoresis and chromatography. Hb Q levels in homozygous cases ranged from 32% to 35%, while in Hb Q heterozygotes the level was 20%. When there was an interaction of beta-thalassaemia heterozygotes the level was 14%, and in interacting beta-thalassaemia homozygotes the levels ranged from 7% to 9%. beta-thalassaemia mutations were characterised in cases showing elevated Hb A2 levels, which were markedly reduced in the majority of cases in which beta-thalassaemia was absent. Hb Q is rare and not a single homozygous case has been reported. However, Hb Q disease showed wide variation in clinical and haematological presentation in the same family.