Over the 6 months recruitment period, all patients with definite PsA who satisfy the inclusion criteria, seen in outpatient visits in the participating centers by one of the investigators, will be asked to participate. It is planned to take place in 6 participating centres in France, 15 other European tertiary rheumatology centers (Germany, Hungary, Ireland, Italy, Norway, Romania, Spain, Turkey and the UK), 4 centers in the USA, 2 centers in Canada, 1 in Brazil, and 2 in Asia (Singapore and Russia).It is planned that in each center, 15-30 patients will be included. The first 15-30 consecutive patients will be selected in each center to reduce bias selection.