Topical photodynamic therapy using methylene blue and 5-aminolaevulinic acid in psoriasis

Photodyamic therapy (PDT) is considered a promising treatment modality for a variety of solid tumours. Recently, beneficial effects of PDT in psoriasis have been described. In this study the effectiveness of topical PDT in psoriasis using different sensitizers was compared with treatment with dithranol. Three patients with chronic plaque-stage psoriasis were treated twice a week with PDT using either methylene blue (MB) or 5-aminolaevulinic acid (ALA) as photosensitizers. An ointment containing 10% MB and another containing 10% ALA were applied topically to defined plaque lesions 5 h before irradiation. Light in the wavelength range 600-700 nm emitted by a 1200 W lamp (prototype Waldman 1200, Waldmann, Germany) was used for treatment (dose 5 J/cm(2), power density 70 mW/cm(2)). The responses of the PDT-treated lesions using MB or ALA were comparable to those of dithranol-treated lesions in all patients. In all areas treated with PDT with ALA a burning sensation was noted, whereas no burning sensation occurred with PDT with MB. This study illustrates the therapeutic effect of PDT in psoriasis. The use of MB as a photosensitizer seemed to minimize the burning sensation, the main side-effect reported so far in topical PDT.