American Medical Association Family Medical Guide - American Medical Association [757]
Psoriasis
Psoriasis is a skin disorder in which new cells in the epidermis (the outermost layer of cells) are produced faster than old cells are shed, causing dead skin cells to accumulate in the affected areas. The cause of psoriasis is unknown, but it is probably a disorder of the immune system. An outbreak of psoriasis is often triggered by emotional stress, skin damage (such as that caused by severe sunburn), excessive consumption of alcohol, or taking some medications. A weakened immune system can trigger outbreaks. Psoriasis usually appears between ages 10 and 30, but it can occur at any age. The condition tends to run in families. Psoriasis can be disabling in the very young or very old if it is not treated. Occasionally a person who has psoriasis will have a form of arthritis (called psoriatic arthritis) that resembles rheumatoid arthritis (see page 918).
Symptoms and Diagnosis
The symptoms of psoriasis include pink or red raised patches of thickened skin covered by white or silvery scales (see page 123). Psoriasis may cause slight itching or soreness but usually causes no discomfort. You may have only one patch of scaly skin or many large ones. The most frequently affected areas are the knees, elbows, and scalp. Less often, patches may appear under the armpits and breasts, on the genitals, and around the anus. When psoriasis occurs on the hands and feet, it is usually in the form of painful cracks or small blisters. In some cases, the nails become thick and pitted and separate from the skin. A person with psoriatic arthritis also has stiff, swollen, and painful joints. Doctors can diagnose psoriasis by its appearance.
Side Effects of Topical Corticosteroids
Inflammation is a major feature of many skin conditions. Topical corticosteroids are medications that are applied to the surface of the skin to prevent or reduce inflammation and are useful for treating a number of skin conditions. If your doctor prescribes a corticosteroid preparation or if you use an over-the-counter topical corticosteroid, use it exactly as directed. Corticosteroids may cause the following adverse reactions:
• Skin reactions (called steroid rashes) These can be flushed skin, pus-filled spots, or a pink, flaky rash. The reactions should disappear when you stop using the corticosteroid.
• Worsening of boils or other skin infections Corticosteroids can make infections worse because they inhibit the immune system.
• A rebound effect The original skin disorder returns (sometimes in a more severe form) when you stop using the medication.
• Permanent changes in your skin If you use a corticosteroid preparation for several months (especially on the face, under the arms, or around the anus or groin), the skin in the affected area thins out, fine blood vessels under the skin can become conspicuous, and marks (similar to the stretch marks of pregnancy) may appear.
• Diminished adrenal gland function Corticosteroids interfere with the function of the adrenal glands by replacing (and preventing the release of) the naturally occurring hormones produced by the adrenal glands, which can be life-threatening.
• Glaucoma and cataracts Using corticosteroid creams around the eyes can cause increased fluid pressure in the eye that can cause eye damage (glaucoma; see page 1042) or clouding of the lens of the eye (cataracts; see page 1041).
Treatment
Psoriasis is a chronic condition with no cure, but treatment usually is successful in clearing up outbreaks. If you have psoriasis, identify and avoid the factors that seem to trigger outbreaks. A number of treatments are available, depending on the severity of the disease. Exposing the skin to sunlight or light from an ultraviolet lamp can help clear up psoriasis. Narrow-band ultraviolet B lightbulbs are more effective than standard ultraviolet lightbulbs. Because a sunburn can make psoriasis worse (and cause skin cancer), your doctor will recommend safe techniques for sunbathing