Psoriatic arthritis (PsA) is a type of chronic inflammatory arthritis that causes joint swelling, pain and stiffness. It’s associated with psoriasis, a skin condition characterized by red, thick, itchy, scaly patches. Both inflammatory arthritis and psoriasis are an autoimmune disease, meaning the immune system mistakenly attacks its own healthy tissues leading to joint inflammation and skin lesions. Approximately eighty per cent of the time, psoriasis precedes the onset of arthritis. PsA can occur at any age, but most commonly presents in people between the ages of 30 and 50.