erythrasma is a superficial skin infection caused by corynebacterium minutissimum interdigital erythrasma is the most common form and is easily confused with tinea pedis the aim of this study was to determine the prevalence of interdigital erythrasma in patients with clinically suspected tinea pedis this study was performed between january 1 2011 and january 31 2012 it included 182 patients who presented with concerns about interdigital lesions all of the patients were examined with a wood s lamp and smears were stained with gram s method direct examination with 20 potassium hydroxide was performed of 182 patients with interdigital lesions 73 40 1 were diagnosed as having erythrasma the mean sd age of the patients with erythrasma was 45 52 10 83 years range 22 70 years most of the patients with erythrasma were women 56 2 the most often clinical finding was desquamation using only wood s lamp examination or gram s staining resulted in 31 42 5 or 14 19 2 positive patients respectively using wood s lamp examination and gram s staining concurrently resulted in 28 positive patients 38 4 interdigital erythrasma is a common condition and can be difficult to differentiate from tinea pedis simple and rapid diagnosis can be made with wood s lamp examination but gram s staining is also a useful method especially in patients with negative wood s lamp examination findings.