• CROHN'S DISEASE
• IBD - GENETICS

The article by Yang et al 1 contributes to the emerging evidence that genetic predisposition to Crohn's Disease (CD) has an ethnicity-specific variation.^s1–s4 The genetic architecture of autoimmune and inflammatory diseases has been subject to recent positive selection in human history, probably driven by the historical exposure to pathogens.2 ^s5–s7 Thus, the differing genetic susceptibilities in East Asians (Koreans and Japanese) vis-à-vis the Caucasoid Euro-Americans might reflect the differences in their historical exposure to predominant pathogens occurring during the historical migrations of anatomically modern humans (AMH) while they populated the globe.^s8 Gene(s) or gene pathways involved in innate immune control of intracellular bacteria (eg, NOD2, ATG16L1, IRGM) and in the IL-23/Th17 pathway are predominant susceptibility loci for Crohn's in Caucasoid, but characteristically not so in East Asians.^{s1, s4} Interestingly, these gene(s) or gene pathways play a primary role in the immune response to human mycobacterial infections, …