Psoriatic arthritis is a spondyloarthropathy which occurs in patients with skin and/or nail psoriasis. Basing its characterization on morphological purposes, several types of arthritis have been described. Alternatively, we propose a simplified classification into three subsets, focusing on the levels of expression of cutaneous and articular elements which devise this syndrome. The first is established psoriatic arthritis which occurs in patients with evident or remittent skin and/or nail psoriasis. Its clinical spectrum consists of the five subsets classically described by Moll and Wright in 1973. The second is psoriatic arthritis "sine psoriasis" which occurs in subjects without psoriasis but with a family history of the disease in first or second-degree relatives. The third is early psoriatic arthritis which consists of an articular involvement of recent onset, occurring in subjects belonging to established or sine psoriasis subsets.