Psoriatic arthritis affects 3 to 7 percent of people with psoriasis, about 1.4 million Americans. In addition to the usual symptoms of psoriasis, they also have joint pain, tenderness, or swelling in the fingers, toes, or spine. Other symptoms include reduced range of motion, morning stiffness, redness and pain of the eye that is similar to conjunctivitis, and nail changes with pitting or lifting of the nail.

Psoriatic arthritis is rarely found in people who do not also have psoriasis. Skin and joint symptoms may flare up or improve simultaneously. Psoriatic arthritis closely resembles rheumatoid arthritis, although people with psoriatic arthritis usually have a negative rheumatoid factor.

This disease can be mild, but it can also be severely deforming and disabling. Like other types of autoimmune disease, psoriatic arthritis has genetic, environmental, and immunologic origins. The gene marker HLA-B27 is present in most people with this disease.

Inflammation of psoriatic arthritis is involved with arachidonic acid pathways and TNF-alpha. New drug therapies, like injectable infliximab and etanercept, aim at lower TNF-alpha levels. A healthful diet plus essential fatty acids help reduce and prevent further inflammation. Evening primrose, borage, and fish oils; turmeric; curcumin; bromelain; and quercetin all work on these pathways.