Clinical characteristics of Japanese patients with psoriatic arthritis: Comparison with East Asian countries.

To determine the characteristics and current status of Japanese patients with psoriatic arthritis, the Japanese Society for Psoriasis Research have started to conduct retrospective questionnaire surveys. The results collected from over a thousand patients with psoriatic arthritis have revealed several characteristics. The newly visited psoriatic arthritis patients accounted for approximately 10% of all new psoriatic patients who visited the dermatology department in many referral centers. The prevalence was nearly 15% of psoriatic patients, which was similar to a recent rheumatology and dermatology study in Japan with a large cohort. There was a male predominance. The mean age of onset for cutaneous psoriasis was in the late 30s, while that of arthritis was in the late 40s. If we compare the precedence of cutaneous psoriasis versus arthritis, the psoriasis precedent group accounted for nearly 75%, while arthritis accounted for 5% of cases. The mean duration in patients who developed psoriasis prior to arthritis was over 10 years, while that in patients preceded by arthritis was less than 5 years. According to the Moll and Wright criteria, polyarthritis type was most common, followed by distal interphalangeal type and oligoarthritis type. Biologics were used in over 50% of psoriatic arthritis patients, and TNF inhibitors were currently used in approximately 70% among biologics. Switching to other biologics or discontinuance was seen in 15%. This review shows the current status of psoriatic arthritis in Japan, as well as a comparison of the prevalence among East Asian countries.