DNA haplotype heterogeneity of β‐thalassaemia in Greece: feasibility of prenatal diagnosis

Abstract

SummaryWe have carried out DNA haplotype analysis of 69 β‐thalassaemia patients in Greece and 42 of the parents using seven standard polymorphic sites. Our data show a high degree of heterogeneity of the chromosomal background in which β‐thalassaemia occurs in Greece, suggesting a high degree of heterogeneity in the β‐thalassaemia mutations involved. Haplotype I is found here to represent 45% of total β‐thalassaemia mutations detected, a proportion well below the 67% reported in earlier studies with Greek‐American patients. Nine different haplotypes are detected and the ones carrying β+ mutations are the majority, including those which are linked to β+ mutations associated with a thalassaemia intermedia phenotype, and which constitute 11% of all haplotypes. One of these haplotypes (—‐ + + +) has never before been reported to occur in non‐Africans, whether in βthal or βA chromosomes, and it is found here to be of African origin rather than the product of recombination. In 21 families haplotype analysis showed that prenatal diagnosis for a second child was feasible in 81% of the cases. Use of the AvaII‐Ψβ polymorphic site as well as the seven standard ones brought this proportion up to 90%.