Psoriasis is a common disorder marked by raised, inflamed lesions that join together to form patches with distinct borders on the skin. The lesions are covered with flaky scales due to the rapid turnover of cells in the epidermis. Psoriasis is not contagious and may be minor or serious. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, about 2 percent of all people in the United States have psoriasis. Most develop the disease before the age of 40.

It is not known what causes the short cycling of skin cells that leads to psoriasis, but a faulty immune system seems to be involved. The development of the disease and flares following remissions usually result from a trigger (e.g., injury, stress, infection, medications).

Psoriasis is recognized by its characteristic lesions. These are raised, swollen, thick patches of red skin covered with flaky scales of dead skin cells that may itch intensely. They vary in size and shape and always have a distinct border. Lesions may occur anywhere, but usually affect the scalp, knees, elbows, naval area, lower back, buttocks or genitalia. Arthritis (joint inflammation) may also be associated.

Psoriasis is usually diagnosed by a physician during a physical examination. If diagnosis is not definite, it can be confirmed with a skin biopsy. Though there is no cure for psoriasis, treatment can help. The goal of treatment is to clear lesions from the skin by reducing the inflammation and slowing down the rapid cell growth and shedding. Treatment may involve phototherapy and/or topical or oral medications, depending on the severity of the psoriasis. Flares can be prevented by identifying and avoiding triggers.