Photodynamic therapy with topical delta-aminolaevulinic acid for the treatment of plantar warts

Treatments currently employed for plantar warts are often painful (electrosurgery, cryotherapy) and not always effective (keratolytic agents). In this paper we investigate the effect of photodynamic therapy (PDT) with topical delta-aminolaevulinic acid (ALA) on plantar warts. In order to remove the superficial hyperkeratotic layer of the warts an ointment containing 10% urea and 10% salicylic acid was applied for 7 days. After gentle curettage, a cream containing 20% ALA was applied under an occlusive dressing for 5 h on 64 warts, while 57 warts (controls) received only the vehicle. Both the ALA-treated warts and the controls were irradiated using a visible light lamp (with a range of 400-700 nm, peaking at 630 nm). The light dose was 50 J/cm(2). Patients were followed-up for 22 months. Two months after the last irradiation session 48 (75.0%) out of 64 ALA-PDT treated warts had resolved. By contrast only 13 (22.8%) of the 57 control warts had done so. During the treatment a few patients complained of a mild burning sensation. The absorption of ALA by the verrucous tissue was demonstrated by in vivo fluorescence spectroscopy. This study shows that topical ALA-PDT can be an alternative treatment for plantar warts. Further studies will be necessary in order to optimize the concentration of ALA and duration of treatment.