Haplotypes of thalassaemic families from the Po river delta: importance for prenatal diagnosis of beta-thalassaemia.

The beta globin haplotypes, corresponding to 50 normal and 50 thalassaemic chromosomes, were determined in 25 families from the Po river delta area who had beta thalassaemia. The haplotypes were obtained by studying the familial segregation of 6 restriction fragment length polymorphisms of the beta globin gene cluster. The results show an almost exclusive presence of 3 haplotypes linked to the beta thalassaemia chromosomes of this area: haplotype I, II and IX according to Orkin's classification. It is therefore possible that only two thalassaemic mutations are present. A wider variety of haplotypes was found to be linked to normal chromosomes. Prenatal diagnosis, by the analysis of polymorphic sites (the 6 plus one other) was possible in 92% of the cases. The probable high homogeneity of the molecular mutations makes the use of specific oligonucleotides practical and applicable to prenatal diagnosis.