Center for Human Genetics and Laboratory Diagnostics, Dr. Klein, Dr. Rost and Colleagues

Crohn’s Disease (Inflammatory Bowel Disease, IBD1) [K50.9]

OMIM numbers: 266600, 605956 (CARD15/NOD2)

Dipl.-Biol. Birgit Busse

Scientific Background

Aside from ulcerative colitis (UC), Crohn’s disease (IBD1) is the most common form of all chronic inflammatory bowel diseases and has an incidence of approx. 1 in 3,000 in Central Europe. While in UC the inflammation is limited to the rectum and parts of the colon, IBD1 may affect the entire intestinal tract. A clear distinction regarding a differential diagnosis is frequently difficult. Studies showed an association between Crohn’s disease and mutations/polymorphisms in the CARD15/NOD2 gene. The gene encodes a receptor which binds bacterial degradation products and therefore regulates the release of antibacterial peptides in the small intestine. Mutations in CARD15/NOD2 impair this receptor function; as a consequence pathogens are not fought off effectively and inflammations develop.

While over 50 sequence variants in CARD15/NOD2 have been associated with IBD1, the polymorphisms R702W, G908R and Leu1007fsX1 represent approx. 82% of all cases of Crohn’s disease associated with CARD15/NOD2. In total, approximately 25-45% of all IBD1 patients are carriers of at least one of these three polymorphisms. Molecular genetic diagnostics aid in the differential diagnostic procedures.