Psoriatic arthritis (PsA) is a type of chronic inflammatory arthritis that affects some people who have psoriasis. Psoriasis is the condition associated with red, itchy, flaky skin patches called scales, usually found on the knees and elbows, and thick, pitted fingernails. Most patients develop psoriasis first and are later diagnosed with psoriatic arthritis, although the joint pain can begin before the psoriasis symptoms appear. Both conditions are believed to be caused by the immune system and the connection between the two can be easily missed.
The National Psoriasis Foundation estimates that up to 30 percent of people with psoriasis also have psoriatic arthritis, and it most commonly strikes between the ages of 30 and 50. There is no cure but there is treatment to ease symptoms, and prevent bone loss and disabling joint damage.