A common skin disease characterized by thickened patches of red, inflamed skin, often covered by silvery scales. It usually appears between ages 10 and 30, tends to run in families, and affects men and women equally. The exact cause of psoriasis is unknown. New skin cells are made about 10 times faster than normal. The excess cells accumulate, forming thickened patches covered with dead, flaking skin. Sometimes, there is also a painful swelling and stiffness of the joints (see arthritis). Psoriasis tends to recur in attacks, which may be triggered by factors such as emotional stress, skin damage, and physical illness. There are different forms of the disorder. The most common is discoid, or plaque, psoriasis, in which patches appear on the trunk, limbs, and scalp. Guttate psoriasis occurs most often in children, and consists of many small patches that develop over a wide area of skin. Pustular psoriasis is characterized by small pustules. In most cases, the condition can be improved with topical treatments, such as those containing corticosteroid drugs and coal tar. Other treatments include dithranol ointment, PUVA, and drugs such as methotrexate. Psoriasis is usually a long-term condition.


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