Background and objective: Standard phototherapy for psoriasis (311 nm UVB or photochemotherapy) exposes the non-affected skin to potentially damaging irradiation. The use of 308 nm XeCl excimer laser allows the selective irradiation of psoriatic lesions. We evaluated its therapeutic effectiveness.
Patients/methods: 28 patients with plaque stage psoriasis were involved in the study, 26 of them could be evaluated. In each patient a single plaque was chosen and then exposed to the laser irradiation thrice weekly. The initial dose was twice the MED (minimal erythema dose); the dosage was increased by one MED every second treatment. The usual dosages were 2-5 MED, while the cumulative UVB dosage was 3.6-15.2 J/cm2. 17 Patients were treated 6 times, while 11 were treated 10 times. The Psoriasis Severity Index (PSI) was calculated for the individual plaque in order to assess the effectiveness of the therapy. The patients were followed regularly for 3 months following treatment, and then checked again at 1 year.
Results: Most patients showed clear improvement. In 90% the PSI at the end of treatment was reduced by at least 50%; in 72% it was only 33% of the pre-treatment value. The results between the patients receiving 6 and 10 treatments were similar. In 6 patients, the psoriatic lesion was still absent after 1 year, while in an additional 7, there had been long term improvement. The most common side effects were erythema and pruritus (100%), blisters (35%) and post-inflammatory hyperpigmentation (80%).
Conclusion: The use of the 308 nm excimer laser is effective for chronic localized psoriasis and may lead to long-lasting remissions.