title: IBD and genetics: new developments.
abstract: BACKGROUND
  Inflammatory bowel disease (IBD) is a complex disorder with an aetiology that is only partly understood. Apart from environmental factors, inheritance contributes to IBD.
  
  
  METHODS
  Family studies show an increased risk among family members of a patient with IBD, particularly among first-degree relatives. In twin studies, concordance for disease type and localization is observed. In genetically isolated groups there is a higher prevalence of IBD. For instance. Ashkenazi Jews carry the highest risk. Further evidence comes from animal species that spontaneously develop IBD. Unlike Mendelian inheritance, in complex genetic diseases like IBD, genes are expected to be low penetrant and therefore less prone to selection, which results in higher expected gene frequencies. NOD2/CARD15, the first gene associated with IBD, is a polymorphic gene involved in the innate immune system. The gene has over 60 variations. Three of these play a role in 27% of patients with CD, with a predilection for patients with ileal disease.
  
  
  CONCLUSIONS
  Genetics plays an important role in unravelling the pathogenesis of IBD leading to possible new therapeutic approaches.
authors.affiliation: Dept. of Gastroenterology and Hepatology, University Hospital Groningen, The Netherlands. L.E.Oostenbrug@int.azg.nl
authors.forename: L E
authors.initials: LE
authors.lastname: Oostenbrug
authors.forename: H M
authors.initials: HM
authors.lastname: van Dullemen
authors.forename: G J
authors.initials: GJ
authors.lastname: te Meerman
authors.forename: P L M
authors.initials: PL
authors.lastname: Jansen
mesh_terms: D002352:Carrier Proteins / Q000235:genetics*; D003424:Crohn Disease / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000235:genetics* / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins; D053473:Nod2 Signaling Adaptor Protein
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein