Psoriasis is a chronic, inheritable skin disease that causes red, scaly (or sometimes pustular) patches, usually on the scalp, trunk, knees and elbows. There is no cure, but treatments (usually prescription creams containing certain steroids and/or treatment with ultraviolet light) can often put the disease in remission. The disease is caused by the noncancerous proliferation of skin cells; the skin cells mature much earlier than normal and rapidly divide, creating thick, irregular, inflamed patches of skin that slough off. The disease most often develops in adults in their late twenties, but can afflict people of any age, from infants to the elderly.