Risk of connective tissue disease, morphoea and systemic vasculitis in patients with hidradenitis suppurativa.

BACKGROUND: Hidradenitis suppurativa (HS) has been associated with auto-inflammatory conditions, yet the risk of developing connective tissue disease (CTD), morphoea and systemic vasculitis has not been well-characterized. OBJECTIVES: We sought to evaluate the risk of developing CTD, morphoea and systemic vasculitis in patients with HS. METHODS: Using claims data, we identified patients with HS and used 2 : 1 risk-set sampling to identify patients without HS. Patients with existing CTD were excluded. Patient follow-up lasted until first occurrence of the following events: the occurrence of outcome (i.e. systemic lupus erythematosus, morphoea, systemic sclerosis, Sjogren's Syndrome and systemic vasculitis), death, disenrolment or end of data stream. Hazard ratios (HR) of developing CTD, morphoea and systemic vasculitis were computed after 1 : 1 propensity score (PS) matching. RESULTS: After 2 : 1 risk-set sampling, we identified 78 122 HS patients and 156 247 non-HS comparators. The mean follow-up was 540 days. After PS matching, HS patients had an increased risk of systemic lupus erythematosus HR = 1.63 (1.31-2.03) and morphoea HR = 2.02 (1.32-3.11), compared to non-HS patients. We did not observe an increased risk for systemic sclerosis HR = 0.90 (0.59-1.44), Sjogren's Syndrome HR = 0.91 (0.73-1.14) or systemic vasculitis HR = 0.87 (0.64-1.20). CONCLUSION: In this population-based study, we observed an increased risk of developing systemic lupus erythematous and morphoea subsequent to a first-recorded diagnosis of hidradenitis suppurativa.