Psoriasis is a common, chronic skin condition that causes red patches on the body. About 1 in 20 individuals with psoriasis will develop arthritis along with the skin condition. In the majority of cases, psoriasis comes before the arthritis. The disorder can be exhibited in a variety of ways. The arthritis is generally mild and involves only a few joints. In a few people, the disease is severe and usually affects the fingers and the spine. When the spine is affected, the symptoms are very much like those of ankylosing spondylitis. The cause of psoriatic arthritis is not known, but genetic factors may play a role. In general, people who have psoriasis have a higher prevalence of arthritis than the general population.
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