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

Abstract

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