Joint inflammation can develop in people who have psoriasis.
Joints commonly involved include the hips, knees, fingers, and toes.
The diagnosis is based on symptoms.
Nonsteroidal anti-inflammatory drugs, disease-modifying antirheumatic drugs (such as methotrexate), cyclosporine, and tumor necrosis factor inhibitors can help.
Psoriatic arthritis resembles rheumatoid arthritis but does not produce the antibodies characteristic of rheumatoid arthritis. Psoriatic arthritis occurs in about 30% of people with psoriasis (a skin condition causing flare-ups of red, scaly rashes and thickened, pitted nails). People with a certain gene (HLA-B27) and those who have affected family members are at increased risk of psoriatic arthritis of the spine. The cause of psoriatic arthritis is unknown.
In psoriatic arthritis, inflammation often affects joints closest to the tips of the fingers and toes, although other joints, including the hips, knees, and spine, are often affected as well. Often, the joints of the upper extremities are affected more. Back pain may be present.
The joints may become swollen and deformed when inflammation is chronic. Psoriatic arthritis affects joints asymmetrically (more on one side of the body than the other), more so than rheumatoid arthritis, and involves fewer joints. Tendons or ligaments can become inflamed where they attach to bone around the joints (called enthesitis). Some people who have psoriatic arthritis also have fibromyalgia, which causes muscle pain, joint stiffness, and fatigue.
The psoriasis rash may appear before or after arthritis develops. Sometimes the rash is not noticed because it is hidden in the scalp, navel, or creases of the skin such as between the back of the buttocks and thigh. The skin and joint symptoms sometimes appear and disappear together and sometimes they do not. Sometimes the skin symptoms are more severe than the joint symptoms, and sometimes the joint symptoms are more severe.
The diagnosis of psoriatic arthritis is made by identifying the characteristic joint inflammation in a person who has arthritis and psoriasis. Doctors also ask people whether they have a family history of psoriasis.
Treatment of psoriatic arthritis is aimed at controlling the rash and relieving the joint inflammation. Several drugs that are effective in treating rheumatoid arthritis (see Rheumatoid Arthritis (RA) : Drugs for Rheumatoid Arthritis) are also used to treat psoriatic arthritis, particularly nonsteroidal anti-inflammatory drugs (NSAIDs), disease-modifying antirheumatic drugs (DMARDs—especially methotrexate), the immunosuppressant cyclosporine, and biologic agents.
Biologic agents are made from living organisms and inhibit certain chemicals involved in the immune system. They include tumor necrosis factor (TNF) inhibitors given by injection or infusion (adalimumab, etanercept, infliximab, certolizumab pegol, and golimumab); ustekinumab, secukinumab, and ixekizumab given by injection; apremilast and tofacitinib taken by mouth; and abatacept given by injection or infusion. TNF inhibitors are particularly effective for psoriatic arthritis.