Geographic and ethnic distribution of beta-thalassemia mutations in Uttar Pradesh, India.

We have studied the geographic and ethnic distribution of mutations in 376 subjects who were carriers of beta-thalassemia, and identified the mutations in 365 chromosomes. The majority of the beta-thalassemia carriers were of Uttar Pradesh (India) origin. Their pattern of mutations differed from the other states of India and from those families who had migrated from Pakistan. The frequency of the IVS-I-5 (G-->C) and 619 bp deletion mutations were 64.3 and 2.5%, respectively, among families originating from Uttar Pradesh, compared to a prevalence of 37.5 and 27.5%, respectively in the population of Pakistani immigrants. Of the 10 common Asian Indian mutations, only eight were observed in subjects studied from different parts of India. By use of the amplification refractory mutation system along with DNA sequencing techniques, the mutations were successfully identified in 97.1% of subjects, while 11 cases (2.9%) still remain to be characterized by single strand conformation polymorphism and sequencing analyses. The application of this knowledge has facilitated the successful implementation of the program of genetic counseling and prenatal diagnosis of beta-thalassemia, thus helping to avoid the birth of an affected child in India.