Ethnicity Differences in Genetic Susceptibility to Ulcerative Colitis: A Comparison of Indian Asians and White Northern Europeans

Background:Studies in Caucasian populations have identified a number of genetic associations with ulcerative colitis (UC), but reports from other ethnic groups have been limited. Recent studies from India have reported an association with UC and a single polymorphism (SNP) in CARD15/NOD2 (SNP5, rs2066842), which has not been reported in Caucasian UC cohorts. In addition, strong genetic associations with SNPs in the HLA region have been reported in Indian UC populations. However, there have been no reports on the frequency of HLA class II alleles in Indian populations with inflammatory bowel disease to examine whether the associations differ from other ethnic populations. Methods:Genotyping was performed for 137 Indian UC patients for HLA class II alleles (HLA-DRB1*1502 & HLA-DRB1*0103), IL23R (rs11209026), and CARD15/NOD2 (rs2066842). The genetic data were compared with 204 healthy Indian controls and 50 white European UC patients. Results:The HLA-DRB1*0103 allele was absent in all Indian UC patients and controls in contrast to white European UC patients (9/50: 18%). The HLA-DRB1*1502 allele was significantly more frequent in the Indian UC cohort (29.2%) than controls (17.6%) (P = 0.04) and the allele was absent in the white European cohort. There were no significant differences in the frequency of the CARD15/NOD2 (rs2066842) variant or IL23R (rs11209026) between the different ethnic groups. Conclusions:The HLA-DRB1*0103 allele is rare or absent in the Indian Asian population but HLA-DRB1*1502 is positively associated with UC. Further genetic studies in this population could provide valuable information and may help distinguish the degree of influence of genetic and environmental pathogenic factors.

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