Recent developments in psoriatic arthritis.

Psoriatic arthritis affects 5% to 7% of patients with psoriasis. Genetic, immunologic, and environmental factors play a role in its pathogenesis. The role of inflammatory cytokines has been better defined, and recent immunohistochemical studies of the synovial membranes have shown important differences and similarities between psoriatic arthritis and rheumatoid arthritis. The association of psoriatic arthritis with infection, particularly HIV, remains an interesting observation. The most common clinical presentation appears to be peripheral polyarticular, and extra-articular manifestations including the SAPHO (synovitis, acne, pustulosis, hypertosis, and osteitis) syndrome are not common. Methotrexate and sulfasalazine therapy are effective in patients who do not respond to nonsteroidal anti-inflammatory drugs.