BACKGROUND: Erythrasma is an uncommon vulvar infection, best diagnosed by its 
fluorescence under the Wood lamp. This report shows that despite a negative Wood 
lamp examination, the diagnosis can be made histologically.
CASE: A 42-year-old woman was referred to our clinic with a persistent candidal 
infection. Evaluation included a Wood lamp examination, wet mount, and potassium 
hydroxide test of the affected skin, all of which were negative. A biopsy of the 
area demonstrated rods and filamentous organisms in the keratotic layer 
consistent with a Corynebacterium minutissimum infection. The patient was 
diagnosed as having erythrasma, and she responded to oral erythromycin.
CONCLUSION: Persistent vulvar diseases may be caused by erythrasma despite a 
negative Wood lamp examination. The diagnosis can be made by biopsy of the 
lesion.