The skin becomes inflamed, producing red, thickened areas with silvery scales, most often on the scalp, elbows, knees, and lower back. In some cases, psoriasis is so mild that people don't know they have it. At the opposite extreme, severe psoriasis may cover large areas of the body.
Doctors can help even the most severe cases.
Psoriasis cannot be passed from one person to another, though it is more likely to occur in people whose family members have it. Approximately 150,000 new cases occur each year. The cause is unknown. However, recent discoveries point to an abnormality in the functioning of key white cells in the blood stream triggering inflammation in the skin. Because of the inflammation, the skin sheds too rapidly, every three to four days.