α-Thalassaemia and globin gene rearrangements in French Polynesia

The prevalence of α-thalassaemia and various globin gene rearrangements was determined in 1992 individuals living on 11 islands in French Polynesia. The gene frequencies for α + -thalassaemia (almost exclusively the -α 3.7 III deletion form) range from 5.3% to 19.2%. Haematological indices on 177 heterozygotes and 27 homozygotes for the -α 3.7 III variant showed considerable overlap with indices of normal individuals ; although there was a broad correlation of average indices with α-globin genotype, individual values were a poor indication of genotype. A non-deletion form of α + -thalassaemia (αα Th ), triplicated α genes (ααα) and single zeta gene (-ζ) chromosomes were present at low frequencies (< 1%), whereas triplicated γ gene (γγγ) and triplicated ζ (ζζζ) arrangements were more common (1.1-16.3%). α 0 -thalassaemia, probably introduced from Southeast Asia in the early part of this century, was observed in a number of individuals of Chinese and Chinese/Polynesian ancestry. Because of the high frequency of α + -Thalassaemia on some islands, it therefore seems likely that haemoglobin H disease (resulting from the interaction between α 0 and α + -thalassaemia) must occur in parts of French Polynesia.