Background: The renin-angiotensin system is strictly related to the kallikrein-kinin system and both are involved in many physiological and disease conditions and possibly in the pathogenesis of inflammatory bowel disease (IBD). Angiotensin-converting enzyme (ACE) is the pivotal enzyme of the renin-angiotensin system and the main catabolic enzyme of the kallikrein-kinin system. The ACE I/D (insertion/deletion) is a polymorphism of the gene encoding for ACE: participants who are homozygous for the D allele exhibit higher ACE levels, which in turn appear to play a deleterious role in several diseases.

Objective: To study the prevalence of ACE I/D polymorphism in IBD patients and its possible association with disease features.

Methods: A total of 232 IBD patients, 124 with ulcerative colitis (UC) and 108 with Crohn's disease and 99 healthy controls were genotyped for the ACE I/D polymorphism.

Results: DD, ID and II genotypes distribution did not show significant differences between IBD patients and controls: 42.2 vs. 40.4%, 42.7 vs. 47.5% and 15.1 vs. 12.1%, respectively. No significant difference was observed between Crohn's disease and UC patients. Within UC patients, the presence of DD genotype and the carriage of the D allele were significantly associated with the presence of extraintestinal manifestations: odds ratio (OR) 4.08, 95% confidence interval (CI): 1.62-10.28; P<0.003 and OR=3.07, 95% CI: 1.45-6.48; P<0.003, respectively. No significant association was found with other IBD clinical features.

Conclusions: The ACE I/D polymorphism is not associated with IBDs but the D allele appears to increase the risk of developing extraintestinal manifestations in UC patients.