Early psoriatic arthritis in Japan: Post-hoc analyses from a survey by the Japanese Society of Psoriasis Research.

To determine the characteristics of the early phase of psoriatic arthritis (PsA), we conducted a subanalysis of a retrospective survey of Japanese patients. In this study, we enrolled patients with early onset within either 2 years or 1 year from onset among the 1282 patients with PsA that had previously been reported. Among the total reported PsA patients, 304 (23.7%) were diagnosed with less than 2 years of onset of joint manifestation. The male : female ratio was 1.9:1, mean age at onset of cutaneous psoriasis 40.2 years, and that of joint manifestation 50.3 years. Age of less than 20 years at cutaneous psoriasis onset was observed in 22 cases, while that at joint manifestation was observed in two cases. Plaque-type psoriasis accounted for 90.1%, followed by psoriasis erythroderma (3.9%), pustular psoriasis (3.9%), and nail psoriasis (1.3%). Polyarthritis was the most common joint manifestation (32.9%), followed by distal interphalangeal (DIP) type (29.6%), oligoarthritis type (27.3%), and ankylosing spondylitis type (4.9%). Enthesitis was observed in 27.3% and dactylitis in 61.8%. Biologics were used in 168 cases (55.3%). By contrast, 199 patients (15.5%) were diagnosed within 1 year of onset of joint manifestation, among whom polyarthritis was the most common (30.7%). Biologics were used in 50.8%. In conclusion, the present study showed that the frequency of early PsA within 2 years of onset accounted for 23.7%, and those within 1 year of onset was 15.5% among the Japanese patients with PsA. Polyarthritis was the most common in early PsA patients.