Since Alibert1first drew attention to the association of psoriasis and arthritis, in 1822, there have been numerous papers on the subject, usually describing single cases. Many attempts have been made to define the entity which has been variously called arthropathic psoriasis, psoriatic arthropathy, arthropathia psoriatica, and psoriatic arthritis. Some definitions have required a reasonable amount of synchronous activity, as evidenced by remissions and relapses in arthritis and cutaneous manifestations,2arthritis restricted to the distal interphalangeal joints,3or, conversely, a peculiar destructive form of arthritis associated with psoriasis.4Hensch5defined it as an atrophic arthritis following long continued and uncontrolled psoriasis, while Dawson6felt that the cutaneous lesions and joint changes must both be atypical. Most published reports have dealt with cases fulfilling one or other of these diagnostic criteria, and broad surveys of the general field of concomitant psoriasis