The triplicated α gene locus and β thalassaemia

S ummary . In five families, the coinheritance of β thalassaemia and an additional α gene ( ααα/αα ) has been observed. Among the β thalassaemia heterozygotes, no phenotypic effect of the triplicated α gene was detected clinically or at the haematological level. Unexpectedly, however, four out of five β thalassaemia homozygotes with the ααα/αα 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 ααα gene arrangement acting as an α thalassaemia allele.