APACHE Cohort (A Psoriatic Arthritis CoHort)

Method:APACHE is a prospective national multicentre (30) cohort including and following during 10 years patients with a first peripheral arthritis in the past year, attributing to a PsA according to the treating rheumatologist. 425 patients will be included during a 4 years period before the follow-up. Standardized visits are planned throughout the 10 years follow-up, permitting the collection of various data: * clinical data * Patients Reported Outcome * usual lab parameters * plasma, serum and urines * Baseline and one year RNA, DNA * peripheral X-Rays, Ultrasounds and MRI at different time points Those visits have non interventional character (no therapeutic decision will be taken) Those collected data will allow submissions of many research projects to the scientific committee of the cohort.