Around 10 - 25% of patients diagnosed with inflammatory bowel disease have a first-degree relative who also has the disease [6]. When geographical backgrounds are considered, the same study identified that the disease is less frequent in African-Americans and Hispanics, whereas Ashkenazi Jews are more susceptible compared to non-Jews. Some clinical studies aimed at identifying the relationship between NOD2 and Crohn’s disease in twins show a concordance rate of 20 - 50% in monozygotic vs. 10% in dizygotic twins [35-37]. This evidence concerns the gene NOD2 and Crohn disease.