Arthritis Foundation and You

Psoriatic Arthritis

Most people don't realize that there are over 100 types of arthritis in existence. One of the less well-known forms of this disease is known as psoriatic arthritis. What is psoriatic arthritis? As its name indicates, psoriatic arthritis is associated with psoriasis, the common skin condition characterized by inflammation of the skin, scaling, and red raised patches of skin. It is estimated that psoriasis affects approximately 2 per cent of the Caucasian population in the United States, although it can occur in people from all backgrounds. The skin condition psoriasis most often affects the scalp, face, navel, tips of the elbows, knees, and areas surrounding the genitals and anus. Health professionals estimate that 10 per cent of all psoriasis patients concurrently develop some form of inflammation in the affected joints. These patients are thus classified as suffering from psoriatic arthritis.

Obviously, one of the major risk factors for developing psoriatic arthritis is the presence of the skin disorder, particularly if it affects the joints. Psoriatic arthritis usually strikes later in life, with most diagnosed cases occurring in the fourth or fifth decades of the patient's life. It appears that gender is not a risk factor, since men and women are affected equally. The majority of patients experience onset of the diseases at different times. It is common that patients develop psoriasis before experiencing symptoms of psoriatic arthritis. Approximately 80 per cent of psoriatic arthritis patients develop psoriasis before the arthritis. However, some patients develop arthritis before the onset of psoriasis. Roughly 15 per cent of psoriatic arthritis patients report the presence of arthritic symptoms before developing psoriasis. In fact, many patients report living with psoriasis for many years before developing any signs of arthritis.

Like other forms of arthritis, psoriatic arthritis is a systematic disease. This means it may affect other areas of the body beside the affected joints. In psoriatic arthritis patients, this means they may be susceptible to other problems. The most commonly affected areas include the lungs, kidneys, eyes, mouth, skin and the heart. In severe forms of the disease, other vital organs may also be affected. Like other forms of arthritis (especially reactive arthritis and spondylitis), psoriatic arthritis patients are more prone to experiencing inflammation in the spine.

What causes psoriatic arthritis? There are many theories, but the cause remains unknown. Most health professionals agree the disease is probably caused by a combination of various environmental factors. Immunity and genetic factors are probably involved as well. There is a gene marker—HLA-B27—that appears in many patients diagnosed with psoriatic arthritis. However, it is not present in all cases. Other genes also appear frequently, furthering the notion that psoriatic arthritis is genetic in nature. Currently there are blood tests available that test individuals for these genes. Another common factor in most psoriatic arthritis cases helps support the notion that the disease is at lease partly immune in nature. Changes in the immune system also appear to be a common factor. In these cases, environmental factors (including the presence of infectious agents) may be responsible for the development of the disease.