If you have psoriasis, an autoimmune skin condition marked by red, flaky patches on the body, you also could be at risk for a certain type of arthritis. Psoriatic arthritis, which causes stiffness, swelling and pain in and around the joints, affects up to 30 percent of people with psoriasis, says the National Psoriasis Foundation. While psoriatic arthritis can develop at any time, it is most common in people between the ages of 30 and 50. This type of arthritis can develop slowly or come on quickly and be severe. Just like psoriasis itself, psoriatic arthritis tends to go through periods of flare-up and remission. Typically, the skin condition precedes the joint disease in 85 percent of patients. Keep in mind that a severe case of psoriasis will not necessarly translate into a severe case of arthritis. Psoriatic arthritis may be treated like other forms of arthritis. Doctors may prescribe anti-inflammatory drugs, antirheumatic drugs, exercise, and complementary therapies. Those who have psoriasis and have begun to experience joint pain and stiffness should talk to a doctor about potential therapies.