General Description

Psoriasis is a very common disorder that affects up to 2 percent of the U.S. population. The condition may have a profound effect on the quality of life of those afflicted. In a study conducted by the National Psoriasis Foundation in 2008, over 60 percent of psoriasis patients expressed feelings of self-consciousness. As most cases begin before age thirty, individuals often require life-long therapy.

Psoriasis is characterized by red patches covered with a silvery, adherent scale. These patches usually do not itch. Any part of the body may become involved, but the most common sites are the elbows, knees, scalp, genitals, and lower back. Psoriasis may also affect the nails, producing tiny pits, discoloration, or marked thickening and distortion. Approximately 15 percent of psoriasis sufferers develop arthritis, which ranges in intensity from mild to crippling.

Psoriasis frequently begins in young adulthood, although childhood cases do occur. The course of the disorder is variable. In the summer months, the condition may improve, particularly following sun exposure. Worsening may follow a long illness or a period of stress.

Causes

The precise cause of psoriasis is as yet unknown, although abnormalities of the immune system play a seminal role. Heredity is also a factor, and people with close relatives who have psoriasis are more likely to develop the condition. Until recently, psoriasis was considered a disease of the skin and joints, and persons with the condition were believed to have the same general health as those without it. This concept has changed drastically during the past few years; recent studies have confirmed that persons with psoriasis are at increased risk of developing high blood pressure, diabetes, and myocardial infarction (heart attack). Whether this is due to the psoriasis, or to the fact that psoriatic patients have a higher rate of obesity, remains unanswered. Evidence is accumulating that the chronic inflammation associated with psoriasis has a deleterious effect on the heart and blood vessels.

Medical Treatments

Although no cure yet exists, psoriasis is a treatable disease, and good to excellent control is usually possible. Most cases respond to steroid ointments, creams, lotions, gels, sprays, or foams of which the most potent are betamethasone, clobetasol, and halobetasol. Trade names include Clobex, Diprolene, Olux, Temovate, and Ultravate. Tar is the oldest therapy and is derived primarily from coal. Drawbacks include odor and staining of both skin and clothes. Drithocreme is a prescription form used primarily on the scalp. Nonprescription tar formulations include the bath oils Balnetar and Cutar, as well as Scytera, a pleasant-smelling foam. Psoriasis of the scalp is commonly treated with tar shampoos (for example, DHS tar, Health911 tar, and T/Gel) in combination with topical steroid lotions, gels, sprays, or foams. A vitamin A derivative, Tazorac cream, is FDA approved to treat psoriasis as are two vitamin D derivatives, Dovonex cream and Vectical ointment. The combination of Dovonex and Ultravate is called Taclonex.

Natural and artificial ultraviolet light improve many cases of psoriasis. Combining ultraviolet A with the oral medication psoralen (PUVA therapy) may induce lengthy remission, but this therapy requires close physician monitoring and the use of a specialized light box. PUVA has been linked to the development of skin cancers. Emerging as a light-based alternative to PUVA is narrow-band UVB therapy. This also entails use of a light box, but no oral medication, and is believed to be safer in the long term. Treatments are ideally administered three times per week, and an average of thirty sessions is required to achieve maximum improvement. The excimer laser is approved by the FDA to treat psoriasis and emits a beam of light similar to narrow-band UVB. Multiple sessions are required, and insurance coverage may be an issue.

Individuals with extensive psoriasis who do not adequately respond to topical and/or light treatments may be placed on systemic therapy. The oral retinoid acitretin (Soriatane) is a potent derivative of vitamin A that can significantly reduce the severity of psoriatic plaques. Lesions usually improve within two months of commencing therapy. Since this medication can raise the level of circulating triglycerides (fats), periodic blood testing is required. Like isotretinoin the drug is teratogenic (may cause birth defects) and must be used with extreme caution in females of child-bearing age, and absolutely never by pregnant females

Methotrexate (MTX) is a potent oral medication used for more recalcitrant cases of psoriasis and for psoriatic arthritis. An advantage of MTX is that the entire dose can be taken once weekly. Favorable response is usually noted within six weeks. MTX can induce nausea, a low white blood cell count, and liver damage. Periodic blood testing is mandatory. A liver biopsy is recommended after prolonged use. MTX should not be used by pregnant females or those who cannot curtail use of alcohol.

Cyclosporine (Neoral) is another oral medication commonly used for hard-to-control psoriasis. Response is often rapid, sometimes occurring within two weeks. The drug is taken daily and works by suppressing certain aspects of the immune system. Cyclosporine may raise blood pressure and serum lipid levels. It can also decrease kidney function, necessitating periodic laboratory monitoring.

Biologics are the newest form of psoriasis therapy. Biologics are produced from human or animal protein rather than chemicals. All are administered by injection. Psoriasis is the result of a miscommunication between the immune system and skin. Signals are sent by specialized immune cells (T lymphocytes), inducing skin cells to multiply rapidly. The trigger mechanism for such behavior appears to be a combination of hereditary and environmental factors. Biologics work on the immune level, suppressing or altering the signals.

Biologic Therapy for Psoriasis

Amevive (alefacept): Administered intramuscularly once weekly in a dermatologist’s office. Twelve-week usual course; an additional twelve-week course may be given. Drug may take at least six weeks to start working. Effects may last up to six months. Works by blocking the action of certain immune cells. Periodic blood tests to monitor immune function required.

Enbrel (etanercept): Administered subcutaneously (under the skin) by the patient at home. Approved for both psoriasis and psoriatic arthritis. Initial dosing may be once or twice weekly, then once weekly after three months. Must be taken continuously to maintain improvement. Enbrel works by blocking an immune signal called tumor necrosis factor-alpha. Requires yearly testing to detect tuberculosis.

Humira (adalimumab): Administered subcutaneously by patient at home. Approved for both psoriasis and psoriatic arthritis. A “loading” dose is given the first week, followed by routine dosing every other week. Must be taken continuously to maintain improvement. Humira works by blocking tumor necrosis factor-alpha. Requires yearly testing to detect tuberculosis.

Remicade (Infliximab): Administered intravenously in an outpatient setting several times over the course of a year. Approved to treat severe psoriasis and psoriatic arthritis. Promotes rapid clearing, which may be sustained for months. Approved for both psoriasis and psoriatic arthritis. Remicade works by blocking tumor necrosis factor-alpha. Requires yearly testing to detect tuberculosis.

Simponi (golimumab): A TNF inhibitor that is injected subcutaneously on a once-monthly basis. Approved in 2009 to treat psoriatic and rheumatoid arthritis, the drug also improves lesions of psoriasis. Requires yearly testing to detect tuberculosis.

Stelera (ustekinumab): Pending release in the United States. Administered subcutaneously by patient at home on an infrequent basis. Works by blocking immune signals (interleukin 12, interleukin 23). High response rate. Safety of this agent in comparison to other biologics awaits additional studies.

Psoriasis affects millions of Americans. Recent medical advances ensure that virtually everyone with this condition can be significantly improved, and consultation with a dermatologist is highly recommended for those with this chronic disorder. Individuals with psoriasis are encouraged to contact the National Psoriasis Foundation (www.psoriasis.org).