Genetic association studies have identified approximately 200 loci associated with IBD, with many shared between CD and UC.36,37 Differences in susceptibility alleles exist between ethnic backgrounds with, for instance, NOD2 and IL23R variants over-represented in European populations compared with East Asian populations.34,37 More recently, using high-density genotyping, 45 variants have been fine-mapped as potentially causal for IBD,38 and this approach may aid better understanding of disease mechanisms. Here, IL23R is linked to irritable bowel syndrome.