What Is It?
Psoriatic arthritis is a chronic (long-lasting) disease in which a person with psoriasis develops the symptoms and signs of arthritis joint pain, stiffness and swelling. Psoriasis is a common, inherited skin condition that causes grayish-white scaling over a pink or dull-red skin rash.
Approximately 5% to 10% of the 3 million people who have psoriasis develop psoriatic arthritis. Psoriatic arthritis affects men and women equally and usually begins between ages 30 and 50. However, the disease can also occur in children. Most people have mild symptoms, but in some cases, the symptoms can be quite severe.
Types of Psoriatic Arthritis
Although each type of psoriatic arthritis is somewhat distinct, some people show a blending of symptoms or have more than one type.
Psoriasis can develop before or after the arthritis, but psoriasis develops first in about 75% of cases. A person may begin to get morning joint stiffness before the arthritis is recognized. People who have psoriasis that involves the nails, especially nail pitting, are much more likely to develop arthritis than those without this problem (50% versus 10%).
The cause of psoriatic arthritis is unknown. There is some evidence that infection or trauma can play a role in the development of the disease. For example, psoriatic arthritis seems to flare up in people whose immune systems are affected by human immunodeficiency virus (HIV) infection. Also, heredity seems to play a role. Up to 40% of people with psoriatic arthritis have a family history of skin or joint disease. Certain genes seem to be involved in certain types of psoriatic arthritis. For example, the gene HLA-B27 has been associated with psoriatic spondylitis.
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