Psoriatic arthritis is a form of arthritis that affects some people who have psoriasis — a condition that features red patches of skin topped with silvery scales. Most people develop psoriasis first and are later diagnosed with psoriatic arthritis, but the joint problems can sometimes begin before skin patches appear.
Joint pain, stiffness and swelling are the main signs and symptoms of psoriatic arthritis. They can affect any part of your body, including your fingertips and spine, and can range from relatively mild to severe. In both psoriasis and psoriatic arthritis, disease flares may alternate with periods of remission.
No cure for psoriatic arthritis exists, so the focus is on controlling symptoms and preventing damage to your joints. Without treatment, psoriatic arthritis may be disabling.
Both psoriatic arthritis and psoriasis are chronic diseases that get worse over time, but you may have periods when your symptoms improve or go into remission alternating with times when symptoms become worse.
Psoriatic arthritis can affect joints on just one side or on both sides of your body. The signs and symptoms of psoriatic arthritis often resemble those of rheumatoid arthritis. Both diseases cause joints to become painful, swollen and warm to the touch.
However, psoriatic arthritis is more likely to also cause:
- Swollen fingers and toes. Psoriatic arthritis can cause a painful, sausage-like swelling of your fingers and toes. You may also develop swelling and deformities in your hands and feet before having significant joint symptoms.
- Foot pain. Psoriatic arthritis can also cause pain at the points where tendons and ligaments attach to your bones — especially at the back of your heel (Achilles tendinitis) or in the sole of your foot (plantar fasciitis).
- Lower back pain. Some people develop a condition called spondylitis as a result of psoriatic arthritis. Spondylitis mainly causes inflammation of the joints between the vertebrae of your spine and in the joints between your spine and pelvis (sacroiliitis).
When to see a doctor
If you have psoriasis, be sure to tell your doctor if you develop joint pain. Psoriatic arthritis can severely damage your joints if left untreated.
Psoriatic arthritis occurs when your body's immune system begins to attack healthy cells and tissue. The abnormal immune response causes inflammation in your joints as well as overproduction of skin cells.
It's not entirely clear why the immune system attacks healthy tissue, but it seems likely that both genetic and environmental factors play a role. Many people with psoriatic arthritis have a family history of either psoriasis or psoriatic arthritis. Researchers have discovered certain genetic markers that appear to be associated with psoriatic arthritis.
Physical trauma or something in the environment — such as a viral or bacterial infection — may trigger psoriatic arthritis in people with an inherited tendency.
Psoriasis on the nails
In some cases, psoriasis can cause pitted and deformed nails that are thickened and discolored. Nails may also separate from the nail bed. Several factors can increase your risk of psoriatic arthritis, including:
- Psoriasis. Having psoriasis is the single greatest risk factor for developing psoriatic arthritis. People who have pitted, deformed nails are especially likely to develop psoriatic arthritis.
- Your family history. Many people with psoriatic arthritis have a parent or a sibling with the disease.
- Your age. Although anyone can develop psoriatic arthritis, it occurs most often in adults between the ages of 30 and 50.
A small percentage of people with psoriatic arthritis develop arthritis mutilans — a severe, painful and disabling form of the disease. Over time, arthritis mutilans destroys the small bones in the hands, especially the fingers, leading to permanent deformity and disability. People who have psoriatic arthritis sometimes also develop eye problems such as pinkeye (conjunctivitis) or uveitis, which can cause painful, reddened eyes and blurred vision. They are also at higher risk of cardiovascular disease.