Psoriasis and arthritis.

The relationship of psoriasis and arthritis is controversial. It has been reported that 7 percent of patients with psoriasis have arthritis. In approximately half of these cases, it is a sero-negative inflammatory polyarthritis, two-thirds of which clinically resemble rheumatoid arthritis. A distinctive peripheral arthropathy is displayed by 1 percent of psoriatics. One-fifth of this group, or less than 0.2 percent of psoriatics, suffer deforming arthritis multilans. The epidemiologic, clinical, radiologic, serologic, and genetic evidence for and against psoriatic arthropathy as a unique entity are reviewed. The prognosis of psoriatic arthritis appears to be better than previously suggested. Therapeutic measures are also reviewed.