Familial clustering of Crohn's disease in Israel: prevalence and association with disease severity.

Background: There is limited data addressing the severity of Crohn's disease (CD) in patients with a family history of inflammatory bowel disease (IBD) compared to sporadic cases.

Methods: We investigated the familial occurrence of IBD and its correlation with disease behavior in CD patients attending the Israeli IBD Foundation meeting using a structured questionnaire.

Results: The study group consisted of 181 CD patients with a total of 825 1(st) degree relatives. Positive family history for IBD in a 1(st) degree relative was reported in 30 patients (16%). Nine out of the 360 parents (2.5%) had IBD (4 CD, 5 UC). There were 17 siblings with IBD (15 CD, 2 UC) out of 351 (4.8%). Ten out of 114 (8.8%) offsprings had IBD (6 CD, 4 UC). When two siblings were affected, their respective age of disease onset was strikingly concordant (r = 0.76, p = 0.008). There was no difference between sporadic and familial CD patients in the age of disease onset, the location of disease, proportion of smokers or percentage of Ashkenazi origin. Furthermore, similar proportions of sporadic and familial patients underwent intestinal surgery, had penetrating or obstructive complications or were treated by immunomodulators and/or biologics. There was also no difference in the reported percentage of time with active disease or the number of flare-ups.

Conclusions: The prevalence of familial disease among Jewish CD patients in Israel is at the high range of the rate found in other ethnicities. Having a positive family history of IBD has no impact on the severity of the disease.