COMMENTARY

Genetics of Inflammatory Bowel Disease

Jean-Paul Achkar, MD, Bret A. Lashner, MD, Cleveland Clinic Foundation, Cleveland, Ohio

Disclosures

April 19, 2002

In This Article

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.[5] 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.[5] Within Jewish populations, Ashkenazi (Eastern European) Jews have higher rates of IBD than Sephardic (Middle Eastern, African, or Spanish) Jews.[1]

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.[4]

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.[12]

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