Psoriasis is a chronic skin disease that is classically characterized by thickened, red areas of skin covered with silvery scales. The extent of skin involvement can range from discrete, localized areas to generalized body involvement. The joints, nails, and mucous membranes may also be affected with the disease. Some cases of psoriasis are so mild that people don't know they have it. Severe psoriasis may cover large areas of the body. Dermatologists can help even the most severe cases. Psoriasis is not contagious and cannot be passed from one person to another, but it is most likely to occur in members of the same family. In the United States, two out of every hundred people have psoriasis (four to five million people). There are approximately 150,000 new cases that occur each year.
