Section 5. Bone, Joint, and Muscle Disorders

Chapter 67. Rheumatoid Arthritis and Other Types of Inflammatory Arthritis

Topics: Introduction | Rheumatoid Arthritis | Psoriatic Arthritis | Reiter's Syndrome | Ankylosing Spondylitis

Psoriatic Arthritis

Psoriatic arthritis is a form of joint inflammation that occurs in some people who have psoriasis of the skin or nails.

The disease resembles rheumatoid arthritis but does not produce the antibodies characteristic of rheumatoid arthritis. Psoriatic arthritis occurs in about 7% of people with psoriasis (a skin condition causing flare-ups of red, scaly rashes and thickened, pitted nails (see Section 18, Chapter 203)). A severe form of psoriatic arthritis can occur in some people with AIDS (see Section 17, Chapter 199).

Symptoms and Diagnosis

Inflammation usually affects joints of the fingers and toes, although other joints, including the hips and spine, are often affected as well. The joints may become swollen and deformed when inflammation is chronic. Arthritis often involves joints less symmetrically than in rheumatoid arthritis and involves fewer joints. The joints at the end of the fingers adjacent to the diseased nails may be involved. The skin and joint symptoms sometimes appear and disappear together.

The diagnosis is made by identifying the characteristic joint inflammation in a person who has psoriasis or a family history of psoriasis. There are no tests to confirm the diagnosis, but x-rays help show the extent of joint damage.

Prognosis and Treatment

The prognosis for psoriatic arthritis is usually better than that for rheumatoid arthritis because fewer joints are affected. Nonetheless, the joints can be severely damaged.

Treatment is aimed at controlling the skin rash and relieving the joint inflammation. Several drugs that are effective in treating rheumatoid arthritis are also used to treat psoriatic arthritis. They include gold compounds, methotrexate, cyclosporine, sulfasalazine, and tumor necrosis factor (TNF) inhibitors. Another drug, etretinate (which is used for severe acne), is usually effective in severe cases, but its side effects may be serious. Because etretinate can cause birth defects, it should not be taken by pregnant women. Moreover, etretinate remains in the body for a long time, so women should not become pregnant while taking the drug or for at least 1 year after discontinuing it.

Some people take methoxsalen (psoralen) by mouth and undergo ultraviolet A light (PUVA--ultraviolet light with psoralen) treatments. This combination relieves the skin symptoms and most of the joint inflammation but may not help inflammation of the spine.