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A 78-year-old Black man presents for evaluation of a pruritic rash in the webspace between the first and second toe. The patient reports the rash has been present “on and off for months to years.” The rash has been treated with mometasone 0.1% cream and oatmeal baths, but no therapy has cured the rash. Physical examination reveals a macerated scaly patch of the web space. Wood’s lamp examination reveals coral-red fluorescence.
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Erythrasma is a common skin condition caused by Corynebacterium minutissimum, a gram-positive, non-spore-forming bacterium that is part of the skin flora.1 The bacterium primarily proliferates in the stratum corneum in areas of high moisture and warmth.1
Erythrasma is often asymptomatic but patients can present with mild to moderate pruritus. The rash is characterized by erythematous plaques, brown or red scaly patches, vesicles, blisters, and maceration.2 There are 3 types of erythrasma: interdigital, intertriginous, and disciform. The most common form is interdigital erythrasma, occurring in the web spaces of the toes. It commonly presents with macerated scale.2 The intertriginous form is commonly seen in the inguinal, groin, and axillary regions. Disciform erythrasma can affect any part of the body and is less common, often seen in patients who live in tropical climates.3
Diagnosis of erythrasma can be confirmed by Wood’s lamp examination. All forms of erythrasma will have a coral-red fluorescence on examination with the Wood’s lamp because of coproporphyrin III produced by the bacteria.2,4 To rule out concomitant dermatophyte or candidiasis, a microscopic examination of scales after potassium hydroxide (KOH) preparation can be performed.1,2
Treatment includes topical or oral antibiotics often with clindamycin, erythromycin, and, more recently, mupirocin.4 Most patients with erythrasma will see full resolution with appropriate treatment.1
The patient’s rash responded fully to clindamycin phosphate 1% solution applied once daily for 2 weeks.
Batul Momin is a third-year medical student at the Suwannee branch of Philadelphia College of Osteopathic Medicine; Joseph M. Dyer, DO, is a board-certified dermatologist with extensive experience in general and surgical dermatology.
References
1. Forouzan P, Cohen PR. Erythrasma revisited: diagnosis, differential diagnoses, and comprehensive review of treatment. Cureus. 2020;12(9):e10733. doi:10.7759/cureus.10733
2. Sariguzel FM, Koc AN, Yagmur G, Bert E. Interdigital foot infections: Corynebacterium minutissimum and agents of superficial mycoses. Braz J Microbiol. 2014;45(3):781-784. doi:10.1590/s1517-83822014000300003
3. Tschen JA, Ramsdell WM. Disciform erythrasma. Cutis. 1983;31(5):541-547.
4. Greywal T, Cohen PR. Erythrasma: a report of nine men successfully managed with mupirocin 2% ointment monotherapy. Dermatol Online J. 2017;23(5):13030/qt9zh116s1.
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