Given the association of defensin secretion with the NOD2 genotype [43] and the findings of numerous previous studies including studies from our IBD center demonstrating ileal disease localization in CD patients with NOD2 mutations [37], [46], [47], we also tested for potential gene-gene interaction of CEACAM6 and NOD2. However, we found no evidence for epistasis between these two genes regarding CD susceptibility. The gene discussed is NOD2; the disease is Cowden disease.