Psoriatic arthritis

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis. The classic features of psoriatic arthritis include enthesitis (inflammation of the entheses), synovitis (inflammation of the joint membrane), and dactylitis (sausage-like swelling of the fingers). It particularly affects the peripheral joints, the spine, and the sacroiliac joints. PsA also often presents with nail lesions, which may include small depressions in the nail (pitting), thickening of the nails, and detachment of the nail from the nailbed.

PsA affects people with the autoimmune disease psoriasis in particular, and about 20-30% of patients with psoriasis develop PsA. However, 10-30% of patients who develop PsA do not have psoriasis at the time of diagnosis. It is not clear if the two diseases are distinct disease entities or one disease.

PsA is classified as a type of seronegative spondyloarthropathy, and is a clinical diagnosis. There are no reliable tests for PsA.

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.

PsA occurs in both children and adults, and affects men and women equally.. The condition is less common in people of Asian or African descent.