XmnIGγ-polymorphism in six unrelated Pakistani families with Inv/DelGγ(Aγδβ)° δβ-thalassemia

The XmnI Ggamma-polymorphism (C-T polymorphism at position -158 to the Ggamma-globin gene) was studied in 13 individuals from six unrelated Pakistani families with deltabeta-thalassemia. All of the subjects had the Asian-Indian Inv/Del Ggamma(Agammadeltabeta) degrees that included six heterozygotes, six homozygotes, and one compound heterozygote of deltabeta- and beta-thalassemia. All seven deltabeta-thalassemia heterozygotes (including one compound heterozygote) had the -/+ genotype, whereas all six of the homozygotes had the +/+ genotype. The results strongly suggest a tight linkage between the XmnI Ggamma-polymorphism and the Asian-Indian Inv/Del Ggamma(Agammadeltabeta) degrees . The finding could explain the unusually well-preserved capacity to produce fetal hemoglobin in deltabeta-thalassemia.