This is a common skin condition which is characterized by thick, red skin with flaky, silver-white patches. The patches of scaly skin usually form on the elbows, knees, other parts of the leg, scalp, lower back, face, palms and soles of the feet, and usually itch or feel sore. About a third of people with the disorder experience joint inflammation that produces symptoms of arthritis. The disease may also affect the fingernails, the toenails, and the soft tissues of the genitals, and inside the mouth. Greater than three percent of the population is affected by this disease, or more than five million adults. It occurs in all ages, but primarily affects adults. It is generally a chronic, or long-lasting disease.