Cross‐sectional multicenter observational study of psoriatic arthritis in Japanese patients: Relationship between skin and joint symptoms and results of treatment with tumor necrosis factor‐α inhibitors

Psoriatic arthritis (PsA) is an inflammatory arthritis with as yet unclear pathophysiology. This retrospective, multicenter, cross‐sectional study was conducted in 19 facilities in western Japan and aimed to identify patients’ characteristics and factors that affect the results of treatment with biologic agents. Of 2116 patients with psoriasis, 285 (13.5%) had PsA. Skin manifestations preceded joint manifestations in 69.8%, the onset was simultaneous in 17.2%, whereas PsA preceded skin manifestations in 2.5%. Peripheral arthritis was most common, occurring in 73.7%, compared with axial disease in 21.8%, enthesitis in 23.5% and dactylitis in 35.4%. Patients with severe skin manifestations were significantly younger at onset (P = 0.02) and more frequently had axial disease (P