What is Psoriatic Arthritis?
Psoriatic arthritis is a complication of psoriasis, a chronic skin disease that is characterized by bright pink or salmon-colored scales covering the knees, elbows, chest, back, or scalp. While most people with psoriasis do not develop arthritis, around 15% do. About 75% of people with psoriatic arthritis develop arthritis symptoms only after the skin condition appears, although in some people the arthritis occurs before the skin condition.
Psoriatic arthritis usually develops between ages 20 and 50 and can affect any joint of the body. At least five variations of psoriatic arthritis exist, differentiated according to which joints are involved and whether both sides of the body are uniformly affected (such as one elbow or both elbows). When fingernails are affected by psoriasis, becoming pitted and ridged, the joints at the tips of the affected fingers are especially likely to develop arthritis. Psoriatic arthritis affects everyone differently, as symptoms and their intensity may vary and can also change within individuals as time passes. Psoriatic arthritis, like psoriasis, is lifelong and cannot be prevented.
Symptoms of psoriatic arthritis
Causes of psoriatic arthritis
Although the cause of psoriatic arthritis is unknown, it probably arises from a combination of genetic and environmental factors. An estimated 40% of people with psoriatic arthritis have a family history of either arthritis or psoriasis, suggesting some type of genetic predisposition.
Certain genes may be associated with different kinds of psoriatic arthritis. For instance, the gene HLA-B27 may contribute to psoriatic spondylitis, which affects the spine. Although most people with this gene do not develop psoriatic arthritis, it is found more often in people who develop this condition than in those who do not. Possible environmental factors that could trigger psoriatic arthritis in a genetically vulnerable person include infection and injury. For example, people with HIV are more likely to develop this condition.
Diagnosing psoriatic arthritis
Your doctor will ask about your symptoms and perform a physical examination. Making a diagnosis may be difficult because symptoms of psoriatic arthritis so closely resemble those of other conditions, such as gout and rheumatoid arthritis. Even x-rays may not always be able to pinpoint psoriatic arthritis as the correct diagnosis. Given the challenges, some people may need to undergo further testing, including x-rays, blood tests, and skin biopsy (a procedure during which a small section of skin is removed for future analysis). Your doctor may also remove a small amount of fluid from your inflamed joints in order to rule out other types of arthritis.
Treating psoriatic arthritis
Psoriatic arthritis may only need treatment as symptoms arise. However, if the condition causes chronic inflammation and is left untreated, it can cause permanent joint damage. Psoriatic arthritis affects each person differently. Although it is only a minor irritation for some, for as many as 25% of people who have it, this condition brings excruciating pain and severe joint damage that can lead to physical disability. Treatment enables most people with psoriatic arthritis to control their pain and to limit joint damage.
Treatment usually begins with taking NSAIDs, such as ibuprofen or naproxen, to relieve pain and inflammation. If these prove insufficient, your doctor may recommend that you take a DMARD such as methotrexate, which can also improve the psoriasis, or sulfasalazine. When these treatments do not work well, anti-TNF therapies may be particularly effective (see “Biological response modifiers”). Corticosteroid injections can help control severe inflammation, but oral corticosteroids are used only occasionally, as they tend to trigger a flare-up of psoriasis. If severe joint damage occurs, your doctor may recommend surgery to repair or replace those joints. To treat your psoriasis, your doctor may also recommend topical medications that can be applied to your skin or exposure to ultraviolet (UV) light, although these treatments will not help your arthritis. Exercise is also essential, as it helps to keep joints flexible and prevents muscle weakness and loss.