DELTA-BETA THALASSEMIA IN SOUTHERN ITALY EVIDENCE FOR A SINGLE MUTATIONAL EVENT

Hematological and molecular studies on 32 heterozygotes for G.gamma.A.gamma..delta..beta..degree.-thalassemia from 15 unrelated families from southern Italy are reported. The hematological features of G.gamma.A.gamma..delta..beta..degree.-thalassemia carriers are compared with those of .beta.-thalassemia and Hb Lepore heterozygotes. Striking similarity exists between the phenotypic expression of .beta.-thalassemia and Lepore mutations. Globin gene mapping studies indicated that the molecular lesion underlying .delta..beta.-thalassemia is a large deletion starting from the large intervening sequence of the .delta. gene and extending downstream from the .beta. gene. The possibility that .delta..beta.-thalassemia haplotypes in southern Italy originated from a single mutational event is discussed.