NOD2 and Crohn disease: Sidiq and colleagues have identified that the NOD2 gene product is present in large quantities among Paneth's cells in the ileum; this coincides with the most commonly affected region in Crohn’s disease [23]. A study by Cleynen et al. identified that the age of onset, surgical history of intestinal bowel disease, or extraintestinal manifestations have little or no association, whereas NOD2 has a potential role in the pathology of Crohn’s disease based on the family history and disease location in the gastrointestinal tract [24] (Figure 1).