The molecular basis of a thalassemia in India. Its interaction with the sickle cell gene

Abstract

The a globin genotype of a total of 282 Indians from Orissa state has been analyzed. The overall a thalassemia gene frequency is 0.29, most frequently caused by the -a3.7 and -a4.2 deletions. In one family a novel -a3.5 deletion removing the a1 globin gene with some of its flanking sequences has been found, suggesting further sequence homology of the a globin gene cluster 3' to the a1 globin gene. Patients with sickle cell disease and a thalassemia had higher hemoglobin (Hb) levels, RBC counts, and Hb A2 levels, and lower reticulocyte counts, MCV, MCH, and Hb F levels than those with a normal a genotype. The frequency of splenomegaly was not influenced by the a globin genotype. A higher prevalence of a thalassemia was found in patients = 10 years of age than in the younger group, suggesting a possible advantageous effect of a thalassemia on the survival of patients with sickle cell disease.