Psoriatic arthritis is a chronic disease characterized by inflammation of the skin, or psoriasis, and inflammation of the joints, or arthritis. About ten percent of patients with psoriasis have psoriatic arthritis. Psoriasis is characterized by itchy, raised, red patches of skin, commonly on the elbows, knees, scalp, navel, and genital areas. Psoriatic arthritis commonly affects the knees, ankles, and joints of the feet. The onset of psoriatic arthritis is often in the patient's 40s or 50s.
Psoriasis and arthritis do not usually appear at the same time, and psoriasis appears first in 80% of psoriatic arthritis patients. A person may have symptoms of arthritis or psoriasis alone for twenty years before showing signs of the accompanying condition. Inflammation in body tissues other than the skin and joints, including the spine, eyes, lungs, heart, and kidneys, may also be present. The cause of psoriatic arthritis in unknown, but a gene known as HLA-B27, as well as other gene markers, are common among patients. Sudden changes in the immune system are also a risk factor.
In addition to skin and joint inflammation, acne and pitting or ridges in the nails are common symptoms of psoriatic arthritis. Pain and stiffness in the joints, the back, and the chest can occur. Inflammation usually affects just a few joints at a time, and pain and stiffness are usually worse in the morning.
Psoriatic arthritis is diagnosed clinically, as there is currently no test for the condition. The symptoms of psoriasis and arthritis are treated individually. Psoriasis may be treated with topical applications, corticosteroid injections, oral medication, light therapy, or biologic injections. Arthritis symptoms are treated with non-steroidal anti-inflammatory drugs (NSAIDs) and exercise. Usually, when psoriasis symptoms improve, arthritis symptoms do too, and vice versa.
Other medications may be used in more extreme cases to prevent joint destruction and deformity; these include methotrexate, antimalarial medication such as hydroxychloroquine, oral or injectable gold, sulfasalazine, leflunomide, tumor necrosis factor (TNF) blockers, and corticosteroids. All of these drugs can have serious side effects and are usually only prescribed for severe psoriatic arthritis. Surgical repair of damaged joints, including joint replacement surgery, is sometimes necessary for psoriatic arthritis patients.
