The role of genetics in IBD is well-established, as demonstrated by family and twin studies and further corroborated by the discovery of the first susceptibility gene, NOD2.7 Genome-wide-association studies have identified over 200 loci associated with CD and/or UC.8 Fine-mapping with high-density genotyping has pinpointed 45 causal variants.9 Despite these advances, genetic heritability accounts for only a fraction of IBD cases.10 Here, NOD2 is linked to inflammatory bowel disease.