Psoriatic arthritis is a chronic inflammation of the joints that occurs in some people with a chronic skin and nail condition known as psoriasis. Psoriasis causes flare-ups of raised patches of skin covered with silvery scales. The onset of psoriasis may occur at any age but is most commonly seen between the ages of 15 and 50 years. Psoriatic arthritis can be noted before or after the skin lesions appear.

What is going on in the body?

People with psoriasis may develop arthritis that causes destruction of various joints. The lining of the joint, the synovium, becomes inflamed. It reacts by producing extra synovial fluid, resulting in a swollen joint. The smooth white surface of the joint, the hyaline cartilage, can become thin, worn, and rough.

What are the causes and risks of the disease?

Psoriatic arthritis occurs only in people with underlying psoriasis. Psoriasis occurs more often in people of European ancestry. Approximately 5% to 8% of people with psoriasis will develop this form of arthritis. It affects men and women equally.

While the exact cause of psoriatic arthritis is unknown, several factors are suspected to be triggers for the disease. These factors include the following:

Both psoriasis and psoriatic arthritis flare up in people with HIV, the immunodeficiency disorder associated with AIDS.