The triplicated alpha gene locus and beta thalassaemia.

In five families, the coinheritance of beta thalassaemia and an additional alpha gene (alpha alpha alpha/alpha alpha) have been observed. Among the beta thalassaemia heterozygotes, no phenotypic effect of the triplicated alpha gene was detected clinically or at the haematological level. Unexpectedly, however, four out of five beta thalassaemia homozygotes with alpha alpha alpha/alpha alpha gene complement had the milder clinical condition of thalassaemia intermedia and in at least one case there was evidence to suggest that this might be due to the alpha alpha alpha gene arrangement actin as an alpha thalassaemia allele.