What Is It? Psoriasis is a chronic skin disorder that causes
scaling and inflammation. Psoriasis may develop as a result of
an abnormality in the body's immune system. The immune system
normally fights infection and allergic reactions. Psoriasis
probably has a genetic component. Nearly half of patients have
family members with psoriasis. Certain medications may trigger
psoriasis. Other medications seem to make psoriasis worse in
people who have the disease. Psoriasis causes skin scaling and
inflammation. It may or may not cause itching. There are several
types of psoriasis: Plaque psoriasis. In plaque psoriasis, there
are rounded or oval patches (plaques) of affected skin. These
are usually red and covered with a 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. Inverse psoriasis is a plaque type of
psoriasis that tends to affect skin creases. Creases in the
underarm, groin, buttocks, genital area