Psoriatic arthritis is an autoimmune disorder. The immune system mistakenly attacks healthy tissue. With psoriatic arthritis, the immune system targets the joints and the skin. Most often, those who have psoriatic arthritis have dry, scaly, itchy, or painful lesions (psoriasis) on their skin, but it is possible to have psoriatic arthritis (PsA) without any noticeable skin changes. Symmetric Psoriatic Arthritis Symmetric PsA is the most...