Variants at the 3p21 locus influence susceptibility and phenotype both in adults and early-onset patients with inflammatory bowel disease

Background: To date, a number of high-profile studies have yielded over 50 inflammatory bowel disease (IBD) disease genes/loci. The polymorphisms rs9858542 (BSN) and rs3197999 (MST1), on 3p21 locus, have been found associated with susceptibility to IBD. We aimed to replicate these associations in adult and early-onset cohorts of IBD Italian patients, by analyzing also potential gene-gene interactions with variants in NOD2/CARD15, IL23R, ATG16L1, and IRGM genes, and investigating genotype-phenotype correlation. Methods: In all, 1808 patients with IBD, 855 with Crohn's disease (CD) and 953 with ulcerative colitis (UC), including 539 patients with their initial diagnosis rs9858542 2.5 × 10^-7; P_rs3197999 3.9 × 10^-7), and UC (P_rs9858542 = 3.1 × 10^-4; P _rs3197999 = 8 × 10^-4). Prevalence of these variants was significantly increased in both adult and earlyonset IBD patients. After stepwise logistic regression, the 2 variants were associated in adult UC with distal colitis (P_rs9858542 = 0.013, odds ratio [OR] = 2.04, 95% confidence interval [CI] = 1.16-3.59; Prs3197999 = 0.018, OR 1.9, 95% CI 1.2-3.3), while the rs3197999 variant was inversely associated with occurrence of extraintestinal manifestations in adult CD(P = 0.017, OR 0.6, 95% CI 0.4-0.9). Conclusions: We confirmed the association of BSN and MST1 with IBD susceptibility, either in the adult or the early-onset cohorts. These variants appeared to influence either the distal location of the disease in the UC cohort and extraintestinal manifestations in CD patients.