Psoriasis

What Is It?

Psoriasis is a chronic (long-lasting) skin disorder that causes scaling and inflammation. Psoriasis affects 2% to 3% of all people. It may develop as a result of an abnormality in the body's immune system, which normally fights infection and allergic reactions. Psoriasis probably involves heredity, because up to 40% of patients have family members with the same problem. Certain medications, such as lithium, a medication for bipolar disorder, may trigger psoriasis. Other medications, including beta-blockers, a class of heart and blood pressure medicines, seem to make psoriasis worse in people who already have the disease.

Symptoms

Psoriasis causes skin scaling and inflammation, with or without itching. There are several types of psoriasis:

• In plaque psoriasis, there are rounded or oval patches (plaques) of affected skin. These are usually red and covered with thick silvery scale. The plaques often occur on the elbows, knees, scalp or near the buttocks. They may also appear on the trunk, arms, and legs.

• Inverse psoriasis is a plaque type of psoriasis that tends to affect skin creases, especially those in the underarm, groin, buttocks, genital areas or under the breast. The red patches of inverse psoriasis may be moist rather than scaling.

• In pustular psoriasis, the skin patches are studded with pimples or pustules.

• In guttate (meaning droplike) psoriasis, many dime-sized or smaller red, scaly patches develop suddenly and simultaneously, often in a young person who has recently had a strep throat or a viral upper respiratory infection.

• About 50% of people with skin symptoms of psoriasis also have abnormal fingernails, especially nail thickening or small indentations, called pitting. A type of arthritis called psoriatic arthritis can affect 10% to 20% of all people with psoriasis, and in some people, it occurs before skin changes appear.