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To elucidate the origin and spread of the sickle cell trait into the Portuguese population, we examined nine polymorphic DNA markers within the β globin gene cluster defining the haplotype. The population sample included 64 sickle-cell-gene-bearing individuals from defined Portuguese-speaking white, black, and Asian Indian populations. The nature and geographic distribution of the different βS haplotypes in Portugal suggest that the sickle cell trait has been imported twice: between the eighth and the thirteenth centuries from the Mediterranean basin (in association with the Benin haplotype) and after the fifteenth century from black Africa over an Atlantic route (Senegal and Bantu haplotypes).