What is psoriatic arthritis?
Psoriatic arthritis is a form of inflammatory arthritis characterized by joint pain, swelling, and morning stiffness. It is associated with having psoriasis or a family history of psoriasis. Both psoriasis and psoriatic arthritis are chronic autoimmune diseases – meaning, conditions in which certain cells of the body attack other cells and tissues of the body.
Psoriatic arthritis can vary from mild to severe, it can present in the following ways:
- Oligoarticular, affects four or fewer joints in the body.
- Polyarticular, affecting four or more joints.
- Spondylitis, less common and affecting the spine, hips, and shoulders.
Who is at risk for psoriatic arthritis?
Psoriasis affects 2-3 percent of the population or approximately 7 million people in the U.S. and up to 30% of these people can develop psoriatic arthritis. Psoriatic arthritis occurs most commonly in adults between the ages of 35 and 55; however, it can develop at any age. Psoriatic arthritis affects men and women equally.
It is possible to develop psoriatic arthritis with only a family history of psoriasis and while less common, psoriatic arthritis can occur before psoriasis appears. Children of parents with psoriasis are three times more likely to have psoriasis and are at greater risk for developing psoriatic arthritis. The most typical age of juvenile onset is 9-11 years of age.
What are the symptoms of psoriatic arthritis?
The symptoms of psoriatic arthritis may be gradual and subtle in some patients; in others, they may be sudden and dramatic. It may be mild, affecting only one joint or can be severe, affecting multiple joints. Not all patients experience all symptoms.
The most common symptoms of psoriatic arthritis are:
- Pain or aching, tenderness, and/or swelling in one or more joints - most commonly hands, feet, wrists, ankles, knees.
- Joint stiffness most notable in the morning or with prolonged inactivity such as sitting for a long time.
- Reduced range of motion in affected joints.
- Pain or stiffness in the lower back.
- Tenderness, pain, or swelling where tendons and ligaments attach to the bone (enthesitis), such as the Achilles’ tendon of the heel.
- Swelling of an entire finger or toe with a sausage-like appearance (dactylitis).
- Silver or gray scaly spots on the scalp, elbows, knees, and/or the lower spine.
- Small, round spots called papules that are raised and sometimes scaly on the arms, legs and torso.
- Pitting (small depressions) of the nails.
- Detachment or lifting of fingernails or toenails.
- Inflammation of the eye (iritis or uveitis).
What causes psoriatic arthritis?
The cause of psoriatic arthritis is unknown. Researchers suspect that it develops from a combination of genetic (heredity) and environmental factors. They also think that immune system problems, infection, obesity, and physical trauma play a role in determining who will develop the disease. Psoriasis itself is neither infectious nor contagious.
Recent research has shown that people with psoriatic arthritis have an increased level of tumor necrosis factor (TNF) in their joints and affected skin areas. These increased levels can overwhelm the immune system, making it unable to control the inflammation associated with psoriatic arthritis.