Fetal hemoglobin levels and beta (s) globin haplotypes in an Indian populations with sickle cell disease.

To further explore the cause for variation in hemoglobin F (Hb F) levels in sickle cell disease, the beta globin restriction-fragment length polymorphism haplotypes were determined in a total of 303 (126 SS, 141 AS, 17 S beta(0), 7 A beta, (0) and 12 AA) Indians from the state of Orissa. The beta(s) globin gene was found to be linked almost exclusively to a beta(S) haplotype ( -++-), which is also common in Saudi Arabian patients from the Eastern Province (referred to as the Asian beta(s) haplotype). By contrast, the majority of beta A and beta(0) thalassemia globin genes are linked to haplotypes common in all European and Asian populations (+-----[+/-]; --++-++). Family studies showed that there is a genetic factor elevating Hb F levels dominantly in homozygotes (SS). This factor appears to be related to the Asian beta(s) globin haplotype, and a mechanism for its action is discussed. There is also a high prevalence of an independent Swiss type hereditary persistence of fetal hemoglobin (HPFH) determinant active in both the sickle cell trait and in sickle cell disease.