Psoriatic Arthritis

Psoriatic arthritis is a chronic inflammatory arthritis that affects about 5-25% of patients with psoriasis. The prevalence varies from 20-420 per 100,000 population across the world, except in Japan where it is 1 per 100,000. In about 80% of cases the presence of psoriasis precedes the onset of psoriatic arthritis. There is not a strong correlation between the severity of psoriasis and the development of arthritis, although psoriatic arthritis may be present more frequently in patients with psoriasis attending dermatology clinics, compared to primary care. The prevalence of psoriasis in the general population is estimated at 2-3%. Psoriasis is associated with joint disease in a significant proportion of patients (reported in one study to be 13.8%). The disease is autoimmune-mediated with defined HLA associations (HLA-B27, -B17, -CW6, -DR4, DR7 and others).