Dr. Stefan Weiss

Q: Dear Dr. Weiss, my aunt suffers from psoriasis. A neighbor suggested that she try laser therapy. Can you tell me more about this treatment and how it works?

A: Although there is no cure for psoriasis, there are many treatment options for this genetic disease of the immune system. Patients with psoriasis experience rapid turnover of their skin cells. The result is the skin becomes red, itchy and covered with silver scales.

Laser therapy is the latest evolution of phototherapy - the treatment of disease with light. Phototherapy reduces inflammation by triggering a sequence of cellular events that changes the skin’s immune system. It was first demonstrated as a way to control psoriasis at the Mayo Clinic in the 1920s.

Traditional phototherapy requires repeated applications of either Ultraviolet A (UVA) (320-400 nanometers) or Ultraviolet B (UVB) (290-320 nm) to achieve clinical response. Although without systemic side effects, traditional phototherapy exposes both involved and uninvolved skin to the full spectrum of either UVA or UVB, placing patients at higher risk for developing future skin cancers.

Recently, researchers discovered that the therapeutic range for psoriasis clearing is between 300- and 313-nm. Treatment with UVB light limited within this narrow range has been associated with a more rapid and effective clearing of psoriasis compared to conventional, broad spectrum UVB. Yet, the normal, uninvolved skin, is still unavoidably exposed to UV radiation, with the same potential adverse effects as traditional phototherapy.

Evidence suggests that compared with uninvolved skin, psoriatic plaques can tolerate higher levels of UV radiation. However, because conventional phototherapy exposes uninvolved skin, the energy levels must remain below the therapeutic maximum. Researchers at Harvard’s Wellman Center for Photobiology addressed this limitation, reporting in 1997 the successful treatment of psoriasis with an Excimer laser that directs a precise, 308-nm wavelength of light to the areas of disease, sparing uninvolved skin. The laser allows for the application of therapeutic levels of energy, while maintaining a safety advantage over traditional phototherapy.

The frequency and duration of treatment depends on the extent of patient disease. Although every patient is unique, the most common treatment protocol is twice-weekly for six weeks and the actual treatment times are usually less than 5 minutes. Unlike many other lasers used in medicine, the Excimer laser is pain-free. Patients may experience transient redness, and infrequently, mild blistering at the treated area about 24 hours after therapy. As a medical procedure, laser therapy for psoriasis is covered by most insurance.

The twice-weekly treatment schedule with the 308-nm laser can safely and effectively clear localized plaque-type psoriasis in fewer treatments and with an overall lower cumulative dose of light, than traditional phototherapy, targeted to only the affected areas of the skin, sparing the surrounding uninvolved skin from unnecessary irradiation.

Stefan C. Weiss, MD, FAAD, is a board-certified dermatologist. For more information, visit www.weissskininstitute.com. Weiss Skin Institute, 9980 Central Park Blvd, North, Suite 124 Boca Raton, FL 33428; 561-372-SKIN .