Prevalence and Clinical Characteristics of Psoriatic Arthritis in Japan

Objective. To investigate the prevalence of psoriatic arthritis (PsA) in Japanese patients with psoriasis. Methods. A multicenter, noninterventional, retrospective cross-sectional study was conducted at 3 tertiary care centers in Japan. PsA was diagnosed by rheumatologists based on clinical findings. Prevalence of PsA, clinical characteristics, comorbidities, and treatment patterns were examined. Results. PsA was identified in 431 of 3021 patients with psoriasis, with a mean prevalence of 14.3% (range, 8.8-20.4%). No large differences between these results and previous reports from Western countries were observed in arthritis distribution, skin disease type, or treatment selection. Conclusion. The prevalence of PsA in patients with psoriasis in Japan approaches 20% in some areas, similar to that observed in Western countries, and is higher than previously reported in Asia. Clinical features including age, sex, age at onset, and manifestation patterns were also similar to those reported in the West.