Clinical and genetic factors associated with sacroiliitis in Crohn's disease.

BACKGROUND AND AIM Radiographic sacroiliitis (SI), often asymptomatic, is considered the most frequent extra-intestinal manifestation (EIM) of Crohn's disease (CD). Data on the association of SI with other clinical features of CD are limited. Association of SI with CARD15 polymorphisms has recently been suggested. In a multicenter study, we investigated the association of SI in CD patients with clinical phenotypes, other EIM and CARD15 polymorphisms. METHODS Radiographs of the sacroiliac joints were taken in 251 CD patients from three Belgian university hospitals and scored by two blinded rheumatologists. Clinical features were obtained from medical records. Forty-three percent of patients carried at least one CARD15 polymorphism. RESULTS Sacroiliitis, defined as the presence of at least grade 2 unilateral changes, was diagnosed in 65 of the 244 scorable radiographs (27%). Only 16 of these patients were previously diagnosed with ankylosing spondylitis (AS). HLA-B27 positivity was observed in 53% of patients with AS and 7% of patients with radiographic SI. In univariate and multivariate analysis, associations between the presence of SI and peripheral arthritis (P = 0.005) and between AS and uveitis (P = 0.005) were found. No associations with other recorded clinical features or with CARD15 polymorphisms were observed. CONCLUSION We confirm the high prevalence of radiographic sacroiliitis in a multicenter CD cohort. Uveitis is only associated with AS whereas all patients with SI are more prone to develop peripheral arthritis during their disease course, suggesting similar pathogenetic mechanisms in the development of these EIM. The previously reported association between SI and CARD15 polymorphisms was not confirmed.