title: Review article: Inflammatory bowel disease and genetics.
abstract: BACKGROUND
  Inflammatory bowel disease (IBD) comprising ulcerative colitis (UC) and Crohn's disease (CD) is multigenic disorder. Tremendous progress has been achieved in unravelling the genetic background of IBD. It has led to the discovery of mutations in NOD2 associated with ileal CD and numerous other genes have been found to be associated with IBD susceptibility.
  
  
  METHODS
  A review of the literature on the genetic background of IBD was performed.
  
  
  RESULTS
  It is only partially understood how mutations in NOD2 lead to CD. Mouse models, in vitro data and studies in humans offer conflicting data as regards whether there is a loss or gain of function of NOD2 in CD. Several additional genes have been identified of which only a few are currently being recognized as potential disease causing or disease modifying genes. Promising candidate genes include TLR4, MDR1, NOD1 (CARD4), DLG5 as well as the IBD5 locus including SLC22A4/5.
  
  
  CONCLUSIONS
  Although genetic research has not yet led to a better prediction of the disease course or patient selection for medical therapy, remarkable progress has been made in the understanding of the pathogenesis of IBD. For future genetic research, accurate phenotyping of patients is very important and large population-based cohorts are needed. Eventually, genetic research may be able to classify different disease phenotypes on a more detailed molecular basis and may provide important contributions in the development of new therapeutic approaches.
authors: Department of Gastroenterology and Hepatology, Section Medical Biology, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands. r.k.weersma@int.umcg.nl
authors: R K
authors: RK
authors: Weersma
authors: H M
authors: HM
authors: van Dullemen
authors: G
authors: G
authors: van der Steege
authors: I M
authors: IM
authors: Nolte
authors: J H
authors: JH
authors: Kleibeuker
authors: G
authors: G
authors: Dijkstra
mesh_terms: D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000235:genetics*; D053474:Nod1 Signaling Adaptor Protein / Q000235:genetics*; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics*; D051197:Toll-Like Receptor 4 / Q000235:genetics*
chemical_list: C119067:NOD1 protein, human; C429018:NOD2 protein, human; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D051197:Toll-Like Receptor 4