Psoriasis (say "sor-eye-ah-sus") is a condition that affects your skin and causes thick red marks that look like scales to form. The thick scaling is due to an increase in the number of skin cells. Sometimes pus-filled blisters form. Most of the time, the skin on the elbows and knees is affected, but psoriasis can occur anywhere on the body, including the scalp, fingernails and mouth, and even the skin over the joints.
Psoriasis affects about 2% of the U.S. population, and the incidence is higher among whites than among people of other races. The disease affects men and women equally and, although it may occur at any age, it occurs less frequently after age 40.
Flare-ups are often related to specific systemic and environmental factors but may be unpredictable; they can usually be controlled with therapy.
The cause of psoriasis is unknown, however, it is thought to be caused by abnormally fast-growing and shedding skin cells. The skin cells multiply so quickly, causing the skin to shed every three to four days. Though not contagious, the condition is hereditary. Psoriasis is often recurrent and occurs in varying severities.
A complete medical history and examination of the skin, nails, and scalp are the basis for a diagnosis of psoriasis. In some cases, a microscopic examination of skin cells is also performed.
Blood tests can distinguish psoriatic arthritis from other types of arthritis. Rheumatoid arthritis , in particular, is diagnosed by the presence of a particular antibody present in the blood. That antibody is not present in the blood of patients with psoriatic arthritis.
Treatment depends on the type of psoriasis, extent of the disease, and effect of the disease on the patient's life. No permanent cure exists; all treatments are palliative.
Lukewarm baths and the application of occlusive ointment bases, such as petroleum jelly, or preparations that contain urea or salicylic acid may soften and help remove psoriatic scales. Steroid creams are also useful.
Methods to retard rapid cell production include exposure to ultraviolet B (UVB) light or natural sunlight to the point of minimal erythema. Coal tar preparations retard skin cell growth and relieve inflammation, itching, and scaling.
Topical corticosteroids are the treatment of choice for mild to moderate psoriasis of the trunk, arms, and legs. These drugs decrease epidermal cell growth and reduce inflammation. They may also reduce symptoms by inducing vasoconstriction. Treatment commonly combines topical corticosteroids with emollients, coal tar preparations, and UV light therapy. For many patients, this is an inexpensive regimen that minimizes adverse effects. Topical vitamin D has shown to be as effective as topical steroids.
Mild psoriasis involving the extremities may be relieved by 0.025% triamcinolone acetonide ointment. Facial, groin, or axillary plaques may respond to 1 % desonide cream or alclometasone dipropionate. More potent topical preparations, such as 0.1 % betamethasone valerate or 0.1 % triamcinolone acetonide, may be prescribed for moderate psoriasis.
Anthralin may help large plaques that don't respond to coal tar or topical corticosteroid preparations. Methotrexate, a drug that inhibits cell replication, may relieve severe, unresponsive psoriasis. Acitretin is a potent retinoic acid derivative that may be used for psoriasis that is resistant to other drugs or treatments. It's especially effective for treating pustular and erythrodermic psoriasis and may also relieve extensive plaque-type psoriasis. However, the disease commonly recurs within 2 months after the cessation of therapy.
Patients with severe chronic psoriasis may use the Goeckerman treatment, which combines topical coal tar treatment with ultraviolet A (UVA) or UVB light therapy. The regimen is used monthly during flare-ups; it may also be used to treat chronic, resistant plaques for extended periods. The Ingram technique is a variation of this treatment, using anthralin instead of coal tar. A modified Goeckerman treatment combines UVB light therapy with topical drugs, such as coal tar preparations, corticosteroids, or kerolytic agents. This therapy may relieve psoriasis more quickly than the standard Goeckerman treatment, but remission may be briefer. A photochemotherapy program called PUVA combines administration of psoralen, either orally or topically, with exposure to UVA light. Cyclosporine (Neoral), an immunosuppressant, is used for severe widespread psoriasis and results in dramatic clearing.
Low-dose antihistamine therapy, oatmeal baths, emollients (perhaps with phenol and menthol), and open wet dressings may help relieve pruritus. Aspirin and local heat help alleviate the pain of psoriatic arthritis; severe cases may require nonsteroidal antiinflammatory drugs.
Therapy for patients with psoriasis of the scalp typically consists of a coal tar shampoo, followed by the application of a steroid lotion while the hair is still wet. No effective treatment exists for psoriasis of the nails. The nails usually improve as skin lesions improve.
At this time, not enough is known about psoriasis to prevent its occurrence. Patients who have experienced a psoriasis flare-up with strep throat should be treated using antibiotics at the first sign of infection.
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