OBJECTIVEThe aim of this study was to determine the prevalence of psoriatic arthritis (PsA) in the patients with plaque psoriasis and to give recommendation for the diagnosis of PsA for dermatologists.METHODSA systematic search was performed in Pubmed, Cochrane and Embase databases. The key-words used from the Medical Searching Heading (MeSH) were: 'Psoriasis', 'Arthritis, Psoriatic', 'Uveitis' and 'Dactylitis'. We selected cross-sectional epidemiological studies written in English or French between January 1980 and October 2009.RESULTSThe initial literature search identified 2171 references. Based on abstract reading and exclusion of studies not written in English or French, and without control group, the final selection included 20 epidemiological studies. With the eight studies using rheumatologically validated criteria, the prevalence of PsA among psoriasis patient spanned a wide range from 7% to 26%.CONCLUSIONPsoriasis arthritis may affect up to 24% of psoriasis patients. Dermatologist should be aware of main clinical sign of PsA to promote earlier recognition and treatment of PsA.