Photodynamic action of red light for treatment of erythrasma: preliminary results

Background: Erythrasma is a superficial cutaneous infection caused by Corynebacterium minutissimum and is characterized by fluorescence under Wood's light (UV) because of the presence of porphyrins. These molecules are photosensitizing and we propose to assess efficacy of red light that activates porphyrins (photodynamic reaction) in treatment of this pathology. Objectives: Assessment of effects of photodynamic action of red light for treatment of erythrasma without exogenous photosensitizing molecules. Methods: Thirteen patients with erythrasma were treated by one illumination (80 J/cm(2)) by red light (broad band, peak at 635 nm) without exogenous photosensitizing molecules. Disappearance or reduction of extent of lesions were observed 2 weeks later. If lesions were still present, a second irradiation was conducted with the same method. Results: Preliminary results are presented. As a result of red light irradiation, we noticed a complete recovery for three patients and, in most other cases, reduction of extent of lesions (mean: -29% after one session). The treatment was well tolerated. Conclusion: We report first cases of photodynamic treatment of erythrasma. There are other reports of clinical applications of antimicrobial action of photodynamic therapy in dermatology (acne vulgaris, leishmaniasis, warts, etc.). But there are few applications without addition of exogenous photosensitizing agent. The originality and interest of our study is to use spontaneous presence of porphyrins in the lesions. This technique seems to be an interesting alternative, inexpensive and easy, for the treatment of this localized infection. But an optimal method is still to be determined to improve efficacy.