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/cm2) 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.