Psoriasis is a long-lasting autoimmune disease characterized by patches of abnormal skin and in some cases there can be an a associated arthritis. These skin patches are typically red, itchy, and scaly. Psoriasis varies in severity from small, localized patches to complete body coverage. Psoriasis is generally thought to be a genetic disease that is triggered by environmental factors. There is no cure for psoriasis; however, various treatments can help control the symptoms.