Crohn’s disease is a common form of chronic inflammatory bowel disease56. The pathogenic mechanisms are poorly understood, but probably involve a dysregulated immune response to commensal intestinal bacteria and possibly defects in mucosal barrier function or bacterial clearance57. Genetic predisposition to CD is suggested by a λs of 17-35 and by twin studies that contrast monozygotic concordance rates of 50% with only 10% in dizygotic pairs58,59.
