Psoriasis Health Dictionary

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.

psych- A prefix meaning mental processes or activities, as in psychology.

The predisposition to psoriasis is genetic, multiple genes being involved, but postnatal factors such as acute infection, hormonal disturbance, pregnancy and drugs can in?uence or provoke it. The sexes are equally affected and onset is most common in the second or third decade of life.

The psoriatic lesion is dull red, scaly and well de?ned. Scale is shed constantly, either in tiny pieces or as large plaques. The scalp is usually affected but the disease does not cause signi?cant hair loss. The ?ngernails may be pitted or ridged and the toenails grossly thickened. Several clinical patterns occur: in guttate psoriasis, a sudden explosion of multiple tiny lesions may follow a streptococcal throat infection, especially in children. Larger lesions are characteristic of discoid (plaque) psoriasis, the usual adult form. In the elderly the plaques may be mainly in the large body folds – ?exural psoriasis. Rarely, psoriasis may be universal (psoriatic erythroderma), or a sterile pustular eruption may supervene (pustular psoriasis).

Mucous membranes in the mouth and elsewhere are not affected. Psoriasis does not affect internal organs, but in about 1 per cent of subjects an in?ammatory joint disease (psoriatic arthritis) may be associated with the condition.

Treatment There is no absolute cure, but several agents used topically are of value including coal-tar extracts, DITHRANOL, CORTICOSTEROIDS and synthetic derivatives of vitamins A and D. Ultraviolet B phototherapy (and natural sunlight) bene?ts most but not all psoriatics. Systemic therapy, including PHOTOCHEMOTHERAPY, is reserved for severe forms of psoriasis. METHOTREXATE, CICLOSPORIN A and oral RETINOIDS are the most e?ective drugs, but they are potentially dangerous and require expert monitoring.

Patient information may be obtained through the Psoriasis Association.

There is no cure, but first-line treatments include *coal tar, *dithranol, and topical corticosteroids and vitamin D analogues (e.g. *calcipotriol). Narrow-band UVB or *PUVA can also be effective as can systemic therapies, such as *methotrexate, *retinoids, and *ciclosporin. Biological treatments, such as *infliximab, *adalimumab, and *etanercept, are potent but expensive.