Evidence of a Genetic Component for IBD
Genetic factors play an important role in the pathogenesis of the inflammatory bowel diseases, including both ulcerative colitis (UC) and Crohn's disease (CD).[1,2] Evidence includes epidemiologic data demonstrating differences in IBD incidence among different races and ethnic backgrounds, familial aggregation, and high concordance for IBD type in monozygotic vs dizygotic twins.[3,4]
Incidence rates for IBD are highest among whites, and among individuals of Jewish background compared with other ethnic groups.[1,3,4] When a proband presents with IBD, the risk of a first-degree relative developing the disease is higher among Jewish vs non-Jewish populations. The familial risk is especially high among siblings, in whom age-adjusted cumulative incidence for Jewish compared with non-Jewish individuals are 16.8% vs 7.0%, respectively, for CD and 4.6% vs 0.9%, respectively, for UC; P = .01. Within Jewish populations, Ashkenazi (Eastern European) Jews have higher rates of IBD than Sephardic (Middle Eastern, African, or Spanish) Jews.
Reports of familial clustering of IBD date back to the 1930s.[6,7] A family history is the single greatest known risk factor for the development of IBD, with at least a 10-fold increased risk compared with the population-based incidence rates.[1,8,9] Among IBD patients, up to 20% will have a family history of IBD. A positive family history is more common with CD than UC, and relatives of patients with CD have a higher risk of developing IBD than do relatives of patients with UC, suggesting a stronger genetic influence for CD.
Twin studies demonstrate greater concordance for IBD among monozygotic twins compared with dizygotic twins.[10,11] Furthermore, the rates of concordance among monozygotic twins are higher for CD than UC, again suggesting that the genetic influence is stronger in the case of the former.
© 2002 Medscape
Cite this: Genetics of Inflammatory Bowel Disease - Medscape - Apr 22, 2002.