Genetic association of nonsynonymous variants of the IL23R with familial and sporadic inflammatory bowel disease in women.

Purpose: To replicate the association of IL23R R381Q (rs11209026) with inflammatory bowel disease (IBD), examine the effect of the two nonsynonymous variations, Q3H and L310P, on IBD, and to study gender distribution of these variants in IBD patients.

Results: IL23R R381Q was associated with Crohn's disease (CD) (P = 0.010), but not with ulcerative colitis (UC); L310P was associated with UC (P = 0.004), but not with CD; no association was observed for Q3H with CD or UC. A female-specific association of R381Q with CD (P = 0.041), and of L310P with UC (P = 0.008) was observed.

Conclusion: We replicated the association of IL23R R381Q with CD but not UC, and we observed an association of L310P with UC, but not CD, in a central Pennsylvania population. Further analysis of the distribution of IL23R variants revealed that these effects were largely female-specific. The results suggest that IL23R R381Q confers protection against CD and that L310P confers protection against UC in females.