Rheumatoid arthritis and pyoderma gangrenosum: a population-based case-control study

Background The association between pyoderma gangrenosum (PG) and rheumatoid arthritis (RA) was not investigated in the setting of controlled studies. The risk of PG among patients with RA is not established. Objective The study aims to evaluate the magnitude of the association between RA and the subsequent development of PG. Additionally, we aimed to characterize patients with RA-associated PG relative to other patients with PG. Methods A population-based case-control study was conducted comparing PG patients (n = 302) with age-, sex-, and ethnicity-matched control subjects (n = 1497) with respect to the presence of RA. Logistic regression models were utilized for univariate and multivariate analyses. Results The prevalence of RA was greater in patients with PG than in control subjects (4.7% vs. 1.5%, respectively; P < 0.001). More than threefold increase in the odds of PG with RA (OR, 3.29; 95% CI, 1.66-6.50) was noted. This association retained its statistical significance following a sensitivity analysis excluding RA cases diagnosed up to 2 years prior to PG (OR, 2.72; 95% CI, 1.25-5.91) and after adjusting for confounding factors (adjusted OR, 2.80; 95% CI, 1.23-5.86). RA preceded the diagnosis of PG in the majority of patients by a mean (SD) latency of 9.2 (7.4) years. Patients with RA-associated PG were older relative to the remaining patients with PG (62.2 [15.0] vs. 53.4 [20.9] years, respectively; P = 0.006). Conclusions RA increases the odds of developing PG by more than threefold. Physicians managing patients with RA should be aware of this increased burden. Patients with RA may be advised to avoid additional precipitating factors of PG.