Prevalence and Predictors of Inflammatory Arthritis in Hidradenitis Suppurativa.

Hidradenitis Suppurativa (HS) is a chronic, debilitating, auto-inflammatory condition often associated with inflammatory arthritis, significantly impacting patients' quality of life. Early diagnosis of both conditions is crucial for optimal management. The objective of this study was to determine the prevalence and factors associated with the development of inflammatory arthritis among HS patients. A cross-sectional study was conducted between November 2021 and February 2023 at an academic dermatology centre in Canada. Adult patients with HS were consecutively sampled, and 52 patients consented to participate and completed assessments. Variables examined included age, sex, HS severity, treatment, ethnicity, family history, lifestyle factors and comorbidities. The main outcomes were rheumatologist-confirmed inflammatory arthritis diagnosis and associated risk factors. Among 52 patients (24 males, 28 females; mean age: 37.4 years), 12 had inflammatory arthritis. Multivariate analysis revealed that Blacks (OR = 0.10, p < 0.001, CI: 0.026-0.343) and Asians (OR = 0.02, p < 0.001, CI: 0.005-0.109) had lower inflammatory arthritis odds compared to Whites. Every 1-year increase in age at HS onset correlated with a 1.17-fold increase in the odds of developing inflammatory arthritis (OR: 1.17, p < 0.001, CI: 1.12-1.24). Smoking (OR = 0.01, p < 0.001, CI: 0.002-0.49), hypertension (OR: 0.23, p = 0.04, CI: 0.057-0.930) and depression (OR: 0.12, p < 0.001, CI: 0.041-0.330) reduced inflammatory arthritis odds. White ethnicity and older age at HS onset were positively associated with inflammatory arthritis, while smoking, hypertension and depression were negatively associated. These findings suggest a distinct subset of HS patients with inflammatory arthritis that warrant further prospective studies. This study contributes to the understanding of inflammatory arthritis in HS patients and emphasises the importance of rheumatology referral during dermatologic clinic visits.