The molecular basis for the clinical diversity of beta thalassaemia in Cypriots.

Much of the clinical variability in the course of homozygous beta thalassaemia in the Cypriot population can be accounted for by the interaction of alpha thalassaemia and by the existence of different molecular forms of beta thalassaemia. Most severe forms of the disorder result from the homozygous state for the common Mediterranean type of beta thalassaemia. One particularly mild form of beta thalassaemia, which also occurs in other Mediterranean populations, results from a single base change at position 6 in the first intervening sequence of the beta-globin gene. These observations provide a basis for the development of a programme for first-trimester antenatal diagnosis using oligonucleotide probes.