[Interdigital erythrasma: clinical, epidemiologic, and microbiologic findings]

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.

The aim of this study was to determine the frequency of erythrasma in patients with interdigital lesions.

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.

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 %).

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.