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Itchy Skin, Flaky Skin? - Maybe Some Light Might Help

New York (Oct 1, 2011)

Psoriasis, a lifelong skin condition, incites the skin to form inflamed, itchy, flaky patches, often on the knees, elbows, scalp, hands, feet, or lower back. Psoriasis symptoms wax and wane from mild and bearable to severe and debilitating – and for some people terribly embarrassing – depending on the seasons, the rise and fall of stressors, and whether plaques are in a highly visible spot.

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One of the most well-known psoriasis sufferers was John Updike, who wrote that the condition caused him to turn away from jobs such as "salesman, teacher, financier, movie star – that demand being presentable" to become instead "a writer in ink who can hide himself and send out a sort of surrogate presence." Updike's fans may be grateful for his career choice, but others with severe cases of psoriasis understand the profound effect its often highly visible symptoms can have on lives.

"Psoriasis has a mind of its own. We can treat but not cure it," said Elizabeth Knobler, M.D., a dermatologist and Director of Phototherapy at NewYork-Presbyterian/Columbia University Medical Center. "Some people with psoriasis are more bothered by it than others."

Elizabeth Knobler, M.D.
Elizabeth Knobler, M.D.

The underlying cause of the disease is an autoimmune disorder that drives skin cells to divide, mature, and die at a rate as much as seven times higher than normal. The rapidly regenerating skin thickens as dead skin cells pile up, and these inflamed areas, or plaques, begin to shed masses of white flakes. As part of the inflammatory process plaques also develop a network of new blood vessels, and T cells, a type of white blood cell, accumulate and trigger the release of other inflammatory factors such as cytokines, lymphokines, and interleukins. The inflamed patches can sting, burn, bleed, and itch intensely. Some people with psoriasis also have a form of arthritis similar to rheumatoid arthritis. Recent studies have also revealed an association between psoriasis and metabolic syndrome with its associated risks for heart disease and diabetes mellitus. Psoriasis affects about 1 to 2 percent of people worldwide.

Forms of Treatment

Dermatologists tailor their treatment approach to each patient, depending on his or her level of discomfort with the itching, pain, or disfigurement they experience. They often begin treatment of mild cases of psoriasis, in which plaques cover less than 5 percent of the body, with a combination of topical agents that can include moisturizers, corticosteroids, vitamin D analogs, and retinoids, Dr. Knobler said.

Horatio F. Wildman, M.D.
Horatio F. Wildman, M.D.

Psoriasis that covers more than 6 to 8 percent of the body is considered moderate to severe, explained Horatio Wildman, M.D., a dermatologist at NewYork-Presbyterian/Weill Cornell Medical Center. "For these patients we tend to use phototherapy first." Narrow-band UVB, light with wavelengths between 311-312 nanometers, is a safe and effective form of phototherapy. "Patients treated with narrowband UVB have a very low risk of a sunburn reaction and current data has not shown an increased risk of skin cancer," he said. "Due to its excellent safety profile, it is a first line therapy for children and pregnant women with moderate to severe psoriasis."

Patients undergoing phototherapy visit the dermatologist two to three times each week, and after six to eight weeks they may begin to notice considerable benefits, Dr. Wildman said. At these visits patients undress and get into a light box, "which is like a freestanding closet lined with fluorescent bulbs," Dr. Knobler explained. Dermatologists follow specific guidelines on how much light patients should be exposed to, depending on the extent of their psoriasis and their skin type, she said. "The goal is to give a dose that is just below that which would cause a sunburn – this is called the sub-erythrogenic dose," Dr. Wildman added. John Updike self-treated his psoriasis with phototherapy by moving to a coastal town where he could sunbathe from spring to fall, and with annual winter trips to the Caribbean.

How Light Therapy Works

Psoriasis develops when the immune system is overactive, and phototherapy is theorized to work by suppressing specific immune functions. "Psoriasis is a T-cell mediated disorder, and UVB works by decreasing the number of inflammatory cells," Dr. Wildman explained.

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In patients who have very thick plaques, dermatologists sometimes use a combination treatment called PUVA – psoralen plus UVA. Psoralen is a photosensitizing agent derived from a plant in the Middle East, Dr. Knobler said. It is totally inactive unless exposed to specific UVA light (320-400 nanometers). Patients take a psoralen pill an hour and a half before treatment. "It is deposited in the skin, and then they go into a lightbox with specific UVA bulbs in it." When psoriasis plaques develop on the palms and soles of the feet, dermatologists apply psoralen ointment to the affected areas. The palms and soles are then exposed to UVA light in a special hand and foot box, said Dr. Knobler.

Dermatologists at NewYork-Presbyterian/Weill Cornell now use PUVA less often for psoraisis said Dr. Wildman, cautioning that PUVA has more potential side effects than narrowband UVB. "PUVA worked well for psoriasis and some patients may obtain a remission for months, however it raises the risk of melanoma, squamous cell cancer, and cataracts, and patients are photosensitized for a day." PUVA still has a role, he said, for psoriasis patients with darker skin or whose plaques are very thick, and for other skin conditions such as mycosis fungoides.

Horatio F. Wildman, M.D., is an Assistant Attending Dermatologist at NewYork-Presbyterian/Weill Cornell Medical Center and an Assistant Professor of Dermatology at Weill Cornell Medical College.

Elizabeth Knobler, M.D., is the Director of Phototherapy at NewYork-Presbyterian/Columbia University Medical Center and an Associate Clinical Professor of Dermatology at Columbia University College of Physicians and Surgeons.

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