Psoriasis is a chronic, genetically determined inflammatory disease, characterized by an immunomediated pathogenesis, which affects approximately 1-3% of the population. Various modalities have been used for psoriasis treatment, including ultraviolet (UV) radiation. Narrowband UVB (311 nm) phototherapy is a well-established, widely used and highly efficient treatment for psoriasis, but a big disadvantage is that large areas of unaffected skin are irradiated along with the psoriatic lesions.
This investigation evaluates a 308-nm excimer laser and a 308-nm excimer lamp in comparison with 311-nm narrowband UVB in the treatment of patch psoriasis by using two different dose-increase schemes.
Fifteen patients with plaque psoriasis were enrolled in the study (first regime). Three different psoriatic lesions were treated with the 308-nm excimer laser, the 308-nm excimer lamp or 311-nm narrowband UVB three times per week. UVB doses were increased slowly and stepwise (1, 1, 2, 2, 3, 3, ...multiple MEDs). Sixteen patients were enrolled in the second regime. Two plaques were treated with the 308-nm excimer laser or with the 308-nm lamp with an accelerated scheme (2, 2, 4, 4, 6, 6, ...multiple MEDs) three times per week. We increased the UVB doses every second treatment (first and second regime) during the whole treatment. If blistering occurred, the blistered plaque was not treated on the next scheduled treatment. At every third visit and 1, 2 and 4 months after the last treatment a Psoriasis Severity Index (PSI) score was assigned in both regimes.
Using Friedman analysis, the PSI scores did not show a statistically significant difference (P > 0.05) comparing 308-nm laser therapy, 308-nm lamp therapy and 311-nm narrowband therapy after 10 weeks in the first regime. The mean number of treatments to achieve clearance was 24. With the accelerated scheme, clearance could be achieved with fewer treatments and with half the cumulative dose of the first regime. Nevertheless, the side-effects such as blistering and crusting were also increased.
Both 308-nm light sources can clear patch psoriasis in a similar manner to standard phototherapy, with the advantage of the ability to treat exclusively the affected skin and with a reduced cumulative dose, thus perhaps reducing the long-term risk of carcinogenicity.