ALPHA-THALASSEMIA AND GLOBIN GENE REARRANGEMENTS IN FRENCH-POLYNESIA

The prevalence of alpha-thalassaemia and various globin gene rearrange ments was determined in 1992 individuals living on 11 islands in Frenc h Polynesia. The gene frequencies for alpha(+)-thalassaemia (almost ex clusively the -alpha(3.7)III deletion form) range from 5.3% to 19.2%. Haematological indices on 177 heterozygotes and 27 homozygotes for the -alpha (III)-I-3.7 variant showed considerable overlap with indices o f normal individuals; although there was a broad correlation of averag e indices with alpha-globin genotype, individual values were a poor in dication of genotype. A non-deletion form of alpha(+)-thalassaemia (al pha alpha(Th)), triplicated alpha genes (alpha alpha alpha) and single zeta gene (-zeta) chromosomes were present at low frequencies (<1%), whereas triplicated gamma gene (gamma gamma gamma) and triplicated zet a (zeta zeta zeta) arrangements were more common (1.1-16.3%). alpha(0) -thalassaemia, probably introduced from Southeast Asia in the early pa rt of this century, was observed in a number of individuals of Chinese and Chinese/Polynesian ancestry. Because of the high frequency of alp ha(+) -Thalassaemia on some islands, it therefore seems likely that ha emoglobin H disease (resulting from the interaction between alpha(0) a nd alpha(+)-thalassaemia) must occur in parts of French Polynesia.