Not only does the number of epidermal cells increase, but also the rate of epidermal cell proliferation is accelerated. The lesions of psoriasis begin as red, scaling papules that coalesce forming oval or round plaques. These plaques are easily distinguishable from the normal surrounding skin. The scales are silvery white and bleed when removed. Scales may become dense, however when a scale is in folds of skin it appears as only a red, smooth plaque with a macerated surface.
Psoriasis can develop at a site of physical trauma such as surgery, sunburn, or scratching.
Pruritis that accompanies it can be highly variable. Psoriasis can occur on any part of the body, however, the most common places include the elbows, knees, scalp, gluteal cleft, fingernails, toenails, and it usually avoids the palms, soles, and face. Psoralen can be administered orally or topically. It is activated by the UVA light and works by inhibiting DNA synthesis, thereby decreasing cellular proliferation. Since there is no cure for psoriasis, PUVA is an efficacious method of controlling this disabling disease.