Psoriasis Diagnosis,Topical Treatments, Light Therapy

by Food and Drug Administration (FDA)

(Page 2 of 4)

Diagnosis and Treatment

No single test exists to diagnose psoriasis, but a dermatologist can usually determine it by the appearance of the skin and by looking at an individual's personal and family medical history. In some cases, a specialist will confirm the diagnosis by examining a small piece of skin (biopsy) under a microscope.

Psoriasis treatments fall into three categories: medications externally applied to the skin (topical), ultraviolet light applied to the skin (phototherapy), and medications taken by mouth or injected (systemic).

Topical Treatments

Topical lotions, ointments, creams, gels, and shampoos for the skin and scalp are prescribed for mild-to-moderate cases of psoriasis or in combination with other treatments for more severe cases. FDA-approved prescription topicals to treat psoriasis include corticosteroids, retinoids, calcipotriene, and coal tar products. These drugs slow down skin cell production and reduce inflammation.

Corticosteroids are synthetic drugs that resemble naturally occurring hormones. Side effects may include thinning of the skin and stretch marks at the area where the topical is applied. Corticosteroids may also suppress the adrenal glands' production of natural steroids, which could leave the body susceptible to disease.

Retinoids are derivatives of vitamin A and calcipotriene is a synthetic form of vitamin D. Retinoids and calcipotriene are not the same as over-the-counter vitamin A and D supplements, which have no value for treating psoriasis, says Wilkin. "These topical creams on the skin deliver the vitamin-like chemicals right to where you want them," he says. Skin irritation where the topical is applied may be a side effect. Retinoids are also available by prescription as oral systemic drugs.

Coal tar products can help with scaling, itching, and inflammation but are not used as commonly as some other topicals, says Lindstrom. They are messy, can stain, and have a strong odor.

Carol Bentson of Washington, D.C., has had plaque psoriasis for more than 30 years, causing "major itching" all over and pain along the scalp line. She has treated it with topical corticosteroids, ultraviolet light, and cortisone injected into her scalp, elbows, toes, and legs. At times, "ointment wouldn't penetrate the areas of heavy plaque buildup, no matter how much I put on," she says.

Bentson has accumulated "sacks of lotions" to treat psoriasis. She would find a topical treatment that worked for a while but then quit working, forcing her to switch to another one.

"With a potent topical steroid, there is a phenomenon called tachyphylaxis," says Craig Leonardi, M.D., associate clinical professor of dermatology at the Saint Louis University Medical School. "Prolonged use can cause down-regulation [decrease] of steroid receptors in cells. The net effect is that the skin becomes less responsive to steroids over time."

Wilkin adds that this unresponsiveness may be a temporary effect. "A patient may need to be off the steroid for a few days or a week and when put back on it, the responsiveness could come back."

Light Therapy

Exposing the skin to ultraviolet (UV) light — either from the sun or an artificial source — sets off a biological process that kills T cells, which slows the buildup of skin cells and reduces inflammation.

Light boxes that emit UV light to treat moderate-to-severe psoriasis and other skin diseases are medical devices that require licensing by the FDA. A person steps into the light box, which is about the size of a telephone booth, while lamps direct the light onto the body.

"Treatment with these devices is complex," says Richard Felten, an FDA chemist and senior medical device reviewer. The physician must determine an individual's sensitivity to UV and adjust the light emissions for the most effective treatment with the least risk of side effects, he says. Side effects may include burning, darkened skin, premature aging, and skin cancer. Three to five treatments per week for several weeks or months may be needed to get the psoriasis under control, followed by weekly maintenance treatments.

Light therapy, or phototherapy, is usually done in the physician's office or a medical facility that has the devices, says Felten. "The FDA has cleared some devices for home use under certain conditions and with a doctor's prescription," he says. Home devices include handheld devices for scalp psoriasis and stand-alone light boxes for other areas of the body.

Light therapy usually involves a short wavelength of ultraviolet light, called UVB. For people with resistant moderate-to-severe psoriasis, a combination of an oral or topical drug called psoralen and a longer wavelength ultraviolet A (UVA) light is used. This treatment is called "psoralen plus UVA" (PUVA).

"Psoralen makes the patient more sensitive to the UVA," says Lindstrom, "so once they've taken a dose of psoralen, a smaller dose of UVA is needed to treat them." Patients must be very careful to protect both skin and eyes for 24 hours after psoralen use to prevent damage, she says.

The FDA has also approved a special type of laser, an excimer laser, as a phototherapy device to treat mild-to-moderate psoriasis. "These lasers can deliver a much more controlled beam of light to small areas of the affected skin," says Felten.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.