In contrast to the explosion of information on the epidemic of type 2 diabetes, there are only scanty studies on T1DM in Indians. The incidence of T1DM in India is not clear, with older reports providing widely varying estimates. In recent reports from United Kingdom, the incidence of T1DM in children of south Asian ranges from 14-20/100,000/year and is increasing. In view of large number of children in India (nearly 40 million <18 years), this implies that India may harbor one of the largest populations of T1DM in the world. In studies in the sub-continent, the high degree of genetic heterogeneity, and entities such as fibro-calcific pancreatic diabetes which present in a similar manner to T1DM, need to taken into consideration.
The principal genetic loci predisposing to T1DM in Indians include HLA class 2 and INS. In contrast to the data in other Caucasians, association studies suggest that HLA DR3-DQ2 is the main susceptibility haplotype rather than DR4-DQ8. Preliminary analysis of Indian families (trios) submitted to T1DGC (n=249) also indicate the strongest association with DR3-DQ2, followed by DR4-DQ8 and the INS locus, with possible associations at chr 4, 6q, 10 and 12. At onset of diabetes, Indian children with T1DM have a lower prevalence of islet antibodies, especially IA2 (in one-third). Islet antibody- negative or type 1B diabetes is more frequent at onset (nearly 45%). LADA is also uncommon among north Indians, with 2 large series documenting a prevalence of 1.6-1.9% for GAD antibodies. Environmental triggers to T1DM are not well studied, though nutritional deficiencies (protein, vitamin D), infections and toxins may play a role in the pathogenesis or presentation of T1DM.
In summary, India has one of the largest populations of T1DM world-wide with overall immune-genetic similarities, but also distinctive differences, when compared with other Caucasian populations.