The importance of intestinal microbiota in development of IBD is supported by common experimental mouse models, such as nucleotide-binding oligomerization domain-containing protein 2 (NOD2)-deficiency and IL-10-deficiency which ordinarily develop ileitis when maintained under standard housing conditions but display reduced disease penetrance in specific pathogen-free environments (50–53). Here, NOD2 is linked to hyperinsulinemic hypoglycemia, familial, 4.