Psoriasis – A recurrent chronic disease of the skin characterized by dry, scaly plaques and papules of varying size.

Causes and Incidence

The cause is unknown but is thought to be related to genetic and environmental factors that trigger an overproduction of epidermal cells. The onset typically occurs between 10 and 40 years of age, and the disorder affects 2% to 4% of the U.S. population. Whites are at greater risk than blacks, as are those with a family history of psoriasis.

Disease Process

Three main pathologic components are at work in psoriasis, to varying degrees. An increased miotic rate causes rapid epidermal cell turnover and shortened transit time of the cell from the basal layer to the epidermis. Faulty keratinization of the horny layer causes easy desquamation and diminishes protection for underlying tissue. Dilation of dermal vessels and intermittent discharge of leukocytes into the dermis cause hot, red skin.


The onset is gradual, and the disorder is characterized by chronic exacerbation and remission. The scalp, elbows, knees, back, and buttocks are the most common sites. The nails, eyebrows, axillae, and anal and genital regions may also be affected. The lesions are well-defined, dry, nonpruritic papules or plaques overlaid with shiny silver scales, and they heal without scarring. The skin may be reddened and hot to touch. Affected nails are pitted, discolored, thickened, and crumbly.

Potential Complications

Common complications include psoriatic arthritis and exfoliative psoriatic dermatitis, which can lead to crippling and general debility.

Diagnostic Tests

The diagnosis is based on examination of characteristic lesions.



Topical corticosteroids, keratolytics used in lotion, cream, ointment, or shampoo form to treat lesions; antineoplastic agents for severe recalcitrant disease.

Shortwave or longwave ultraviolet light therapy; lubricants to soften skin; exposure to sunlight but avoiding sunburn; stress reduction programs; prevention of mechanical injury to skin; instruction that lesions are not communicable; counseling if body image is affected and to adapt to chronic nature of disease.