Psoriasis is a chronic, autoimmune disease that appears on the skin. It occurs when the immune system sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious.
There are five types of psoriasis: plaque, guttate, inverse, pustular and erythrodermic. The most common form, plaque psoriasis, appears as raised, red patches or lesions covered with a silvery white buildup of dead skin cells, called scale. Psoriasis can occur on any part of the body and is associated with other serious health conditions, such as diabetes, heart disease and depression.
According to the National Institutes of Health, as many as 7.5 million Americans have psoriasis.