Autoimmune diseases in first- and second-degree relatives of patients with inflammatory bowel diseases: a case-control survey in Israel.

BACKGROUND: Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic, relapsing, inflammatory diseases of the gastrointestinal tract with unknown etiology. IBD are complex, multi-factorial disorders, in which genetic factors play a major role, the so-called phenomenon of familial aggregation or clustering of IBD. A positive family history of IBD is often reported among CD and UC probands, with percentages depending on the geographic context in which the studies are carried out. Israel is a complex and pluralistic society comprising of two major ethno-national groups (Arabs and Jewish) and, as such, represents a unique living laboratory in which to test the role of genetic factors in the development of IBD as well as of associated autoimmune disorders (ADs). While some studies have found a lower prevalence of ADs among Arabs when compared to Jews, few studies directly compared the two ethnicities.

METHODS: The present case-control study was designed to compare the rate of ADs in first- and second-degree relatives of IBD patients, stratified according to Jewish or Arabic ethnicity.

RESULTS: We found that first-degree relatives of Jews patients had a higher risk of developing ADs (OR=1.89, P=0.0086). Classifying ADs into systemic and local (endocrinological, gastrointestinal, dermatological, and neurological) types, first-degree relatives of Jews patients had a higher OR of developing local ADs (OR=2.12, P=0.0056).

CONCLUSIONS: Israeli Jewish IBD patients had more first-degree relatives with local ADs as compared to Arab patients.