Psoriatic arthritis is a condition in which people with psoriasis — a skin disease characterized by itchy, red patches — also experience arthritis that leads to joint pain, stiffness, and inflammation. Although the arthritis is usually mild with occasional flare-ups, it can become continuous and potentially cause joint damage if untreated.

The signs and symptoms of psoriatic arthritis vary among individuals and may include psoriasis, joint swelling, stiffness or pain, fatigue, "sausage-like" swelling of fingers or toes, nail changes, eye inflammation, and inflammatory bowel disease.

Psoriatic arthritis is diagnosed through a combination of evaluating family history, physical signs like swollen joints and skin lesions, blood tests to exclude similar diseases, and imaging tests to assess joint or spine changes. There is no specific test for the condition.

Psoriatic arthritis has no cure, but effective treatments exist to reduce symptoms, and options vary based on individual severity. Milder cases may use over-the-counter medications and corticosteroid injections, but more severe cases may require disease-modifying antirheumatic drugs (DMARDs) and biologic response modifiers.

The efficacy of various supplements for psoriatic arthritis remains unclear due to limitations in pilot trials, such as small sample sizes and short durations. Some of the supplements studied include vitamin D, omega-3 fatty acids, primrose oil, and curcumin, among others.

Certain foods may trigger symptoms in some people with psoriatic arthritis. Individuals report relief from following popular diets, including gluten-free, low carbohydrate, and Paleolithic diets. Although the effect of specific diets is unclear, weight loss through diet may help control disease symptoms because obesity is associated with increased disease activity.

Acupuncture has shown positive effects on psoriatic arthritis in small studies, and although high-quality evidence is lacking, it is conditionally recommended by the American College of Rheumatology and the National Psoriasis Foundation. Additionally, exercise, yoga, stretching, aqua therapy, and physical or occupational therapy can improve overall health, joint flexibility, and muscle strength.

The exact cause of psoriatic arthritis is not well understood, but both genetic factors and environmental triggers (such as stress, obesity, infection, and injury) have been implicated in its onset. Many people with this condition have family members who also have it, which suggests a genetic link.