The relative absence of the NOD-2 mutation in CD cases in Japan suggests that the role of smoking in IBD is subject to underlying genetic heterogeneity.[52] Environmental factors such as air pollution[53], diet and a Western lifestyle as demonstrated in migrant sub-populations[6] as well as evolving early life feeding patterns and improved hygiene as part of socioeconomic development[12] could be more potent mediators of IBD development.[54,55]. The gene discussed is NOD2; the disease is inflammatory bowel disease.