Psoriatic arthritis

Psoriatic arthritis (PsA) is a long-term inflammatory arthritis that may occur in some people affected by the autoimmune disease psoriasis. The classic features of psoriatic arthritis include dactylitis (sausage-like swelling of the fingers), skin lesions, and nail lesions. Lesions of the nails may include small depressions in the nail (pitting), thickening of the nails, and detachment of the nail from the nailbed. Skin lesions consistent with psoriasis (e.g., red, scaly, and itchy plaques) frequently occur before the onset of psoriatic arthritis but psoriatic arthritis can precede the rash in 15% of affected individuals. It is classified as a type of seronegative spondyloarthropathy.

Genetics are thought to be strongly involved in the development of psoriatic arthritis. Obesity and certain forms of psoriasis are thought to increase the risk.

Psoriatic arthritis affects up to 30% of people with psoriasis. It occurs in both children and adults. Some people with PsA never get psoriasis.

The condition is less common in people of Asian or African descent. It affects men and women equally.