Alpha-thalassemia among tribal populations of Eastern India.

Five hundred and thirteen unrelated subjects belonging to various tribes of West Bengal, Arunachal Pradesh and Assam in Eastern India, were screened for the presence of alpha-thalassemia (thal) gene deletion(s) as a possible cause of unexplained anemia (Hb < 11 g/dL and/or MCH <28 pg, MCV < 78 fL). As reported earlier, beta-globin gene mutant alleles were found with a frequency of up to 20% in some tribes. In the present study, alpha-globin gene deletion alleles were found in 18% of subjects from West Bengal, 3.9% from Arunachal Pradesh and 3.84% from Assam tribesmen. Coexistence of alpha- and beta-globin gene abnormalities was observed in up to 18% of some tribal groups. The high inbreeding rate and lack of appropriate medical care make these populations particularly vulnerable.