Psoriasis is a chronic and long-lasting skin disease characterized by scaling and inflammation. Scaling occurs when cells in the outer layer of the skin reproduce faster than normal and pile up on the skin’s surface.
Psoriasis affects approximately 2.2% of the United States population, or about 7.5 million people. Although the disease occurs in all age groups and about equally in men and women, it primarily affects adults. People with psoriasis may suffer discomfort, including pain and itching, restricted motion in their joints, and emotional distress.
In its most typical form, psoriasis results in patches of thick, red skin covered with silvery scales. These patches, which are sometimes referred to as plaques, usually itch and may burn. The skin at the joints may crack. Psoriasis most often occurs on the elbows, knees, scalp, lower back, face, palms, and soles of the feet, but it can affect any skin site. The disease may also affect the fingernails, the toenails, and the soft tissues inside the mouth and genitalia. About 15% of people with psoriasis have joint inflammation that produces arthritis symptoms. This condition is called psoriatic arthritis.