A chronic disease of the skin consisting of itchy, dry, red patches, usually affecting the scalp or arms and legs. A common chronic skin disease, more common in whites (2% of the population) than in other racial groups, in which red flaky lesions occuroften on the elbows and knees, or in the scalp. May cause nail abnormalities. A chronic skin disease that occurs when cells in the outer layer of the skin reproduce faster than normal and pile up on the skin's surface. This results in scaling and inflammation. An estimated 10 to 30 percent of people with psoriasis develop an associated arthritis called psoriatic arthritis.
More than 4.5 million adults in the United States have been diagnosed with psoriasis, and approximately 150,000 new cases are diagnosed each year.