Erythrasma is a superficial skin disease caused by Gram-positive Corynebacterium 
species. Coral-red fluorescence under Wood's light, strongly suggestive of 
erythrasma, can be attributed to the presence of porphyrins. Fractionated 
porphyrin analysis in erythrasma lesions is yet to be reported. We attempted to 
investigate erythrasma lesions by isolating the responsible bacteria and 
determining their exogenous porphyrin production by HPLC analysis. We observed a 
78-year-old woman with erythrasma who had a well-demarcated slightly scaling 
patch on her left foot, between the fourth and fifth toes. Two kinds of colonies 
on 5 % sheep blood agar were obtained from this lesion. Analysis of the 16S rRNA 
sequence revealed the colonies to be Corynebacterium aurimucosum and 
Microbacterium oxydans. HPLC analysis demonstrated that coproporphyrin III 
(Copro III) levels were clearly elevated, although the amounts of protoporphyrin 
were diminished. These results indicate that the fluorescent substance was Copro 
III. This study supports the view that excess Copro III synthesis by C. 
aurimucosum and M. oxydans leads to accumulation of porphyrin in cutaneous 
tissue, which emits a coral-red fluorescence when exposed to Wood's light.