NOD2 and irritable bowel syndrome: The genetic background is not only associated with susceptibility to IBD but also impacts the community structure of the intestinal microflora24,25 and determines the host immune response to intestinal microflora.26Ethnic differences in IBD susceptibility genes have been reported.27 Thus far, the well-known NOD2/CARD15 gene accounts for up to 20% of CD in the Caucasian population; however, this gene is not associated with CD in the Japanese and Chinese populations.28–30