Psoriatic arthritis is a form of joint inflammation that can occur as a secondary disease in people with psoriasis of the skin. Symptoms include swelling and stiffness of the joints most commonly in joints closest to the tips of the fingers and toes that can develop following the skin rash; however, symptoms of psoriatic arthritis may not appear for many years after the skin rash onset or not at all. As the disease progresses and inflammation becomes chronic, joint deformity may result. Patients already diagnosed with psoriasis of the skin are thought to be genetically predisposed to developing psoriatic arthritis; the specific cause of both the skin rash and arthritis are unknown, but genetic, environmental and immunologic factors can contribute. Treatment is largely based on medications to help relieve joint pain and swelling, and also includes therapies to control the skin rash and exercise to reduce joint stiffness.