Psoriatic arthritis is a type of inflammatory arthritis that occurs in some patients with psoriasis. This particular arthritis can affect any joint in the body, and symptoms vary from person to person. Research has shown that persistent inflammation from psoriatic arthritis can lead to joint damage. Fortunately, available treatments for are effective for most people.

Psoriatic arthritis usually appears in people between the ages of 30 to 50, but can begin as early as childhood. Men and women are equally at risk. Children with psoriatic arthritis are also at risk to develop uveitis (inflammation of the middle layer of the eye). Approximately 15% of people with psoriasis develop psoriatic arthritis. At times, the arthritis can appear before the skin disorder.

What causes psoriatic arthritis is not known exactly. Of those with psoriatic arthritis, 40% have a family member with psoriasis or arthritis, suggesting heredity may play a role. Psoriatic arthritis can also result from an infection that activates the immune system. While psoriasis itself is not infectious, it might be triggered by a streptococcal throat infection, commonly known as strep throat.

To diagnose psoriatic arthritis, rheumatologists look for swollen and painful joints, certain patterns of arthritis, and skin and nail changes typical of psoriasis. X-rays often are taken to look for joint damage. MRI, ultrasound or CT scans can be used to look at the joints in more detail.

Blood tests may be done to rule out other types of arthritis that have similar signs and symptoms, including gout, osteoarthritis, and rheumatoid arthritis. In patients with psoriatic arthritis, blood tests may reveal high levels of inflammation and mild anemia but labs may also be normal. Anemia is a condition that occurs when the body lacks red blood cells or has dysfunctional red blood cells. Occasionally skin biopsies (small samples of skin removed for analysis) are needed to confirm the psoriasis.