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What Is Psoriatic Arthritis?
Psoriatic arthritis is an inflammatory arthritis associated with psoriasis, a chronic skin and nail disease. There are five types of this disease:
- Arthritis involving primarily the small joints of fingers or toes
- Asymmetrical arthritis, which involves joints of the extremities
- Symmetrical polyarthritis, which resembles rheumatoid arthritis
- Arthritis mutilans, which is rare but very deforming and destructive
- Arthritis of the sacroiliac joints and spine (psoriatic spondylitis)
The exact prevalence of each of these forms of arthritis is difficult to establish. Patterns may themselves change with time in individual patients, and some patients may show overlapping features or more than one type. Sometimes arthritis is associated with inflammation of the eyes, or inflammation at the bony sites of attachment of ligaments and tendons, causing local pain, for example at the heels.
The exact cause is unknown, but an interplay of immune, genetic, and environmental factors are suspected. Up to 40% of patients with psoriatic arthritis may have a history of psoriasis or arthritis in family members. Both psoriasis and psoriatic arthritis flare up in the presence of immunodeficiency due to HIV infection (AIDS).
- Psoriatic arthritis affects at least 10% of the 3 million people with psoriasis in the United States.
- It affects men and women equally and usually begins between 30-50 years of age, but can begin in childhood.
- Psoriatic arthritis may precede the onset or the diagnosis of psoriasis in up to 15% of patients.
Skin and nail changes characteristic of psoriasis must be demonstrated before a diagnosis can be made with certainty. Elevated erythrocyte sedimentation rate (ESR), mild anemia, and elevated levels of blood uric acid can be seen in some patients. Gout must be excluded.
Initial treatment of psoriatic arthritis consists of the use of nonsteroidal anti-inflammatory drugs (NSAIDs), but methotrexate may be needed for arthritis that doesn't respond. An antimalarial drug, hydroxychloroquine, may be effective, but some patients experience a flare of their psoriasis. Sulfasalazine has been found to be very beneficial for some psoriatic arthritis patients. Azathioprine may be used in severe cases of the disease.
Corticosteroid injections directly into the joints can be useful. Cyclosporin has been used recently with some good results, but because of kidney side effects, it should be reserved for patients with progressive disease unresponsive to other measures. Proper exercise is very important. Surgery can be helpful in patients who develop joint destruction.