BACKGROUND: Erythrasma is a skin infection which is caused by Corynebacterium 
minutissimum. Interdigital erythrasma is the most common form.
OBJECTIVE: The aim of this study was to detect the frequency and risk factors of 
interdigital erythrasma in patients with clinically suspected tinea pedis.
METHODS: This study was conducted between June and December 2010 and included 
122 patients who had interdigital foot lesions. All patients were examined using 
a Wood's lamp. The smears were stained using Gram's method. Direct examination 
was performed using 20% potassium hydroxide. Sabouraud dextrose agar and brain 
heart infusion agar were used for cultures. Moreover, the demographical 
characteristics of patients, concomitant diseases and clinical findings were 
also recorded. Cases that were found to be positive on Wood's lamp examination 
and/or Gram staining/culture were considered as erythrasma.
RESULTS: The rate of erythrasma was found to be 46.7%. The mean age was 43.6 
years, and the disease was more prevalent in men. The most common clinical 
finding was desquamation. Mycological examination was found as positive in 
40.35% of the patients. No growth was observed in bacteriological cultures. It 
was found that using only Wood's lamp examination or Gram staining resulted in 
11 (9%) and 19 positive patients (15.6%), respectively, whereas using both 
Wood's lamp examination and Gram staining concurrently resulted in 27 positive 
patients (22.1%).
CONCLUSION: Interdigital erythrasma is a commonly seen condition and can 
clinically mimic tinea pedis. A Wood's lamp is a good diagnostic tool, but Gram 
staining, particularly in those with a negative Wood's lamp result, may be a 
useful method.