Alpha-thalassaemia in the north west of England.

Although it is extremely rare amongst the indigenous population, we have previously identified several British individuals with alpha-thalassaemia. It was to be expected that the underlying molecular defect in these individuals would result from racial admixture; however, we found that many of them share a specific, previously reported determinant of alpha-thalassaemia, referred to as --BRIT (Higgs et al. 1985). Several of these individuals with the --BRIT determinant originated from the North West of England and therefore a more extensive survey of individuals from this area was undertaken. We identified 14 individuals with the --BRIT determinant out of 200,000 individuals studied. These, together with all other known examples bring the total number of cases identified to 36. It seems likely that this almost exclusively British determinant of alpha-thalassaemia (--BRIT) has become established through genetic drift in this population.