Quantification of the relationship between pyoderma gangrenosum and Crohn’s disease : a population-based case-control study

Background: Although Crohn’s disease (CD) is an established underlying disease in pyoderma gangrenosum (PG), studies comparing patients with PG and controls with respect to the presence of CD are lacking. Consequently, the relative risk imposed by CD for the development of PG is yet to be elucidated. Objective: The study aims to quantify the magnitude of the association between CD and subsequent development of PG, thus enabling to evaluate the risk of PG with CD. Methods: A matched case-control study was conducted in Israel comparing PG patients (N = 302) with age-, sex- and ethnicity-matched control subjects (N = 1497) regarding the presence of CD. Logistic regression model was used for multivariate analysis. Results: The prevalence of CD was higher in patients with PG than in control subjects (7.0% vs. 0.3%, respectively; p <.001). There was a 28-fold increase in the odds of PG with CD (OR, 28.08; 95% CI, 9.56–82.41). This association was robust to a sensitivity analysis excluding CD cases diagnosed up to 3 years prior to PG (OR, 30.30; 95% CI, 8.82–104.09), and to a multivariate analysis adjusting for confounding factors (OR, 21.57; 95% CI, 7.20–64.58). The median latency between the diagnosis of CD and the development of PG was 8.08 years. Patients with both PG and CD were younger and had a higher prevalence of smoking when compared to other patients with PG. Conclusions: CD increases the odds of having PG by 28-folds. Patients with CD should be advised to avoid additional precipitating factors of PG like pathergy and smoking.