BACKGROUND: Erythrasma is a superficial infection caused by Corynebacterium 
minutissimum and affects the major skin folds and the interdigital regions of 
the feet. It is characterized by erythematous, brown, scaly patches and 
maceration, and exhibits coral-red fluorescence under Wood light.
OBJECTIVE: The aim of this study was to determine the frequency of erythrasma in 
patients with interdigital lesions.
METHODS: An open, prospective, longitudinal, observational study was performed 
in a hospital in Mexico City between March and December, 2006. All patients with 
interdigital lesions were examined with a Wood lamp and direct examination was 
performed with 20 % potassium hydroxide. Cultures were done in Sabouraud 
dextrose agar and brain heart infusion agar, and smears were analyzed. General 
characteristics and concomitant diseases were recorded.
RESULTS: We examined 73 patients, of whom 24 (32.8 %) were diagnosed with 
erythrasma based on coral-red fluorescence under Wood light and identification 
of corynebacteria by Gram staining. The disease was more common in women (83.33 
%) and the mean age of the patients was 43.5 years. The main clinical findings 
were scaling and maceration, and the fourth interdigital web was the most 
commonly affected. Corynebacterium could not be isolated in any of the cases. 
Mycology was positive in 15 cases (62.5 %) and the following microorganisms were 
isolated: Candida (16.6 %), dermatophytes (12.5 %), and Trichosporon (4.1 %).
CONCLUSIONS: Interdigital erythrasma is a common condition and can be easily 
confused with interdigital tinea. It persists if not treated appropriately. 
Rapid diagnosis is easily obtained by examination with a Wood lamp, while 
culture is difficult and unnecessary for diagnosis. The coexistence of 
erythrasma with dermatophytes and Candida should be considered when the 
interdigital webs are affected.