NOD2 and Crohn disease: Roughly 10% of healthy Caucasians carry NOD2/CARD15 variants associated with Crohn's disease however the majority of these people do not develop IBD; carrying a mutation in NOD2/CARD15 confers a three-fold risk of developing Crohn's disease among heterozygotes and a 20-fold increased risk for homozygotes with approximately 5% penetrance (19).