psoriasis

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psoriasis

(sôrī`əsĭs), occasionally acute but usually chronic and recurrent inflammation of the skin. The exact cause is unknown, but the disease appears to be an inherited, possibly autoimmune disorder that causes the overproduction of skin cells. Psoriasis may occur at any age but is uncommon in children. The characteristic lesion is a scaly "mother-of-pearl" patch, appearing anywhere on the body. Involvement may range from a single plaque to numerous patches that cover most of the skin. A variety of treatments are used for patients with mild to moderate cases. Treatments directed at the symptoms include the application of ointments and exposure to sunlight and ultraviolet (UVB) light. Retinoids help stabilize follicular epithelial cells. Vitamin D analogs and metabolites, although effective in treatment, have side effects. Photochemotherapy (psoralen combined with UVA radiation) is also effective, but increases the risk of skin cancer. Alfacept and other drugs that interfere with T-cell (see immunityimmunity,
ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
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) activation, and etanercept, infliximab, and other drugs that block tumor-necrosis factor are effective in many patients with moderate to severe psoriasis.

Psoriasis

 

a chronic recurrent noncontagious skin disease of man. Neuropsychic traumas and metabolic and endocrine disorders play a part in the development of psoriasis. The disease may also be viral or genetic in nature.

Eruptions may appear anywhere on the skin but generally occur on the elbows, knees, sacral region, and scalp. The disease becomes acute with the appearance of small pink-red papules covered with silvery scales that readily slough off. When the papules are scraped, the scales fall off in small particles, revealing a smooth shiny surface underneath. Further scraping produces small drops of blood. The papules rapidly enlarge, often coalescing to form plaques. This process may be circumscribed, disseminated, or generalized (erythroderma psoriaticum). When the papules and plaques reach a certain size, they stop growing and then harden, shrink, and disappear, leaving depigmented or hyperpigmented spots.

There are thus three stages of psoriasis: progressive (appearance and growth of papules), stationary (stable), and regressive (hardening and disappearance of papules). Sometimes the nail plates are affected, and their surface becomes thimble-like. In some patients, the eruptions are accompanied by swelling and tenderness of the joints (psoriasis anthropathica).

Treatment is effected by administering vitamins A, B1, B6, and B12, tranquilizers, and hormones, by means of ultraviolet radiation and application of paraffin and desquamative and resorbing ointments, and by health-resort therapy.

REFERENCE

Mashkilleison, L. N. Chastnaia dermatologiia. Moscow, 1965. Pages 161–216.

I. IA. SHAKHTMEISTER

psoriasis

[sə′rī·ə·səs]
(medicine)
A usually chronic, often acute inflammatory skin disease of unknown cause; characterized by dull red, well-defined lesions covered by silvery scales which when removed disclose tiny capillary bleeding points.

psoriasis

a skin disease characterized by the formation of reddish spots and patches covered with silvery scales: tends to run in families