Phenotypic effect of heterozygous α and β0-thalassemia interaction

Abstract

In this study, we carried out restriction endonuclease mapping in order to characterize the α-globin genotype of 10 Sardinian β0-thalassemia heterozygotes, all of whom presented with normal red blood cell indices and increased HbA2 levels. In 8 of these subjects, we found the deletion of two α-globin genes (-α/-α), and in the remaining two the deletion of a single α-globin gene (-α/αα). In three of these carriers with the (-α/-α)α-globin genotype and in one with the (-α/αα) genotype, we also found the glucose-6-phosphate dehydrogenase (G6PD) defect of the Mediterranean type. On the basis of these findings, we may conclude that the interaction of heterozygous β0-thalassemia with α-thalassemia, due to the deletion of either one or two α-globin genes, may lead to the production of red blood cells with normal indices. The association of the G6PD defect with this thalassemia gene complex may eventually contribute to this effect. We suggest, therefore, that screening programs for heterozygous β-thalassemia in populations where α-thalassemia is also prevalent, should incorporate the determination of HbA2 in the first set of tests.