THE PREVALENCE OF INFLAMMATORY BOWEL-DISEASE IN RELATIVES OF PATIENTSWITH CROHNS-DISEASE

Objective: To determine the prevalence of inflammatory bowel disease ( IBD) in relatives of patients with Crohn's disease. Methods: Postal qu estionnaire supplemented by review of case notes (for all patients). I nterviews (personal or telephone) were carried out to confirm a positi ve family history. Patients: Complete information was obtained from 43 3 adult patients with Crohn's disease. Ages ranged from 17-85 years. M ore than 95% of patients were resident locally. Results: In 78 familie s (18%), at least one first- or second-degree relative also had IBD; t hree relatives were affected in 14 families and four in two families. Both Crohn's disease and ulcerative colitis occurred in these multiply -affected pedigrees. First-degree relatives were affected in 50 famili es (11.5%). Siblings were most affected (33 siblings in 29 families). Crohn's disease (20 siblings) was more common than ulcerative colitis (13 siblings); 19 parents and four offspring were affected. A spouse w as affected in one family only. IBD was not present in families of ado pted Crohn's disease patients. Assuming a population prevalence of 170 /100 000 for IBD, the relative risks for IBD in siblings, parents and offspring of patients with Crohn's disease calculated from these data are, respectively, 24.7, 12.5 and 4.41. Conclusion: These data confirm the increased prevalence of IBD in families of patients with Crohn's disease. Genetic susceptibility appears to be implicated in disease pa thogenesis.