Genetic associations of inflammatory bowel disease in a South Asian population

AIM To estimate prevalence and phenotypic associations of selected inflammatory bowel disease (IBD)-associated genetic variants among Sri Lankan patients. METHODS A case study of histologically confirmed ulcerative colitis (UC) or Crohn's disease (CD) patients with >= 1 year disease duration, who were compared to unrelated, gender-matched, healthy individuals as controls, was conducted at four major centers in Sri Lanka. Phenotypic data of the cases were obtained and all participants were genotyped for 16 selected genetic variants: IL12B:rs1045431, IL23R:rs11805303, ARPC2:rs12612347, IRGM:rs13361189, IL26/IL22:rs1558744, CDH1:151728785, IL10:rs3024505, FCGR2A:rs3737240, PTGER4:rs4613763, IL17REL/PIM3:rs5771069, HNF4a:rs6017342, STAT3:rs744166, SMURF1:rs57809799, LAMB1:rs886774, HLA-DRB5, DQA1, DRB1, DRA:rs9268853, MST1, UBA7, and APEH:rs9822268. The genotypes of all variants were in Hardy-Weinberg Equilibrium (P > 10(-3)). To account for multiple hypothesis testing, P-values < 0.003 were considered significant. RESULTS A total of 415 patients and 465 controls were recruited. Out of the single nucleotide polymorphisms (SNPs) tested, the majority were not associated with IBD in Sri Lankans. Significant positive associations were noted between rs886774 (LAMB1-gene) and UC (odds ratio (OR) = 1.42, P = 0.001). UC patients with rs886774 had mild disease (OR = 1.66, P < 0.001) and remained in remission (OR = 1.48, P < 0.001). A positive association was noted between rs10045431 (IL 12B gene) and upper gastrointestinal involvement in CD (OR = 4.76, P = 0.002). CONCLUSION This confirms the heterogeneity of allelic mutations in South Asians compared to Caucasians. Most SNPs and disease associations reported here have not been described in South Asians.