Purpose: India bears a major burden of homozygous beta-thalassemia. Hemoglobin (Hb) E/beta-thalassemia has been described mainly among Bengalis in Eastern India. Ethnic groups in northeastern India have among the highest known gene frequency for Hb E. However, there are few reports of Hb E/beta-thalassemia from these ethnic groups. This study aims to determine whether the paucity of reports of Hb E/beta-thalassemia from this region are because of underdiagnosis or complete elimination of beta-thalassemia by Hb E.
Populations and methods: The published literature concerning Hb E, beta-thalassemia, and the syndrome of Hb E/beta-thalassemia in Indid, Tibeto-Burman, and Austro-Asiatic ethnic groups in northeast India was analyzed to determine the gene frequency of Hb E and beta-thalassemia for different ethnic groups. The expected cases of Hb E/beta-thalassemia were calculated using the Hardy-Weinberg law.
Results: The Bodo-Kachari have a gene frequency of 0.50 for Hb E, the highest anywhere in the world. There are, however, no reports of beta-thalassemia in this group. Among ethnic groups in which prevalence of Hb E and beta-thalassemia are known, there is a vast discrepancy between the reported number of cases of Hb E/beta-thalassemia and the number predicted by Hardy-Weinberg law. Thus, there are only seven cases of Hb E/beta-thalassemia from northeast India reported in the literature as opposed to 67,332 predicted cases.
Conclusion: A potentially large pool of unsuspected Hb E/beta-thalassemia cases exist in northeast India. The significance of this finding and possible contributory factors are discussed.