PSORIASIS A chronic, recurrent disorder. Classic lesion is a well-marginated, erythematous plaque with silvery-white surface scale. Distribution includes extensor surfaces (i.e., knees, elbows, and buttocks); may also involve palms and scalp (particularly anterior scalp margin). Triggers Infections, such as strep throat or skin infections Injury to the skin, such as a cut or scrape, a