Snapshot A 50-year-old man presents with a rash on his right foot. He reports noticing this rash between his fourth and fifth toe a few days ago, and denies any symptoms related to the rash. He has a past medical history of diabetes managed with metformin, and obesity. He lives in Chicago, where it is currently summer and very humid. On physical exam, there is a erythematous and macerated scaly plaque between his fourth and fifth toe. He is given topical antibiotics for management of this disease. Introduction Clinical definition superficial infection of the skin caused by Corynebacterium minutissimum characterized by maceration and scaly plaques in skin folds Epidemiology demographics higher in soldiers and hospitalized patients rare in children risk factors humid conditions immunocompromised state diabetes obesity hyperhidrosis Etiology infection by gram-positive bacillus, C. minutissimum Pathogenesis C. minutissimum is a part of normal skin flora if conditions are too moist or occlusive, the bacteria can proliferate in the stratum corneum, disrupting the skin and causing maceration and flaky plaques Associated conditions trichomycosis axillaris another condition caused by Corynebacteria Presentation Symptoms may be asymptomatic or pruritic Physical exam location toe webs (most common) scaling maceration of toe web spaces intertriginous (groin or axilla most common) erythematous thin plaques initially red but can progress to brown lesions have overlying fine scaling and wrinkling “cigarette paper”-like Studies Wood’s lamp examination coral-red fluorescence Gram stain of skin scraping gram-positive filaments and rods KOH preparation to rule out simultaneous dermatophyte infection Diagnostic criteria typically based on clinical exam and history Wood’s lamp exam can confirm diagnosis Differential Seborrheic dermatitis negative Wood’s lamp examination greasy scaling Tinea versicolor negative Wood’s lamp examination Treatment Medical topical therapy indication localized disease drugs clindamycin/erythromycin fusidic acid imidazole antifungals has activity against some gram-positive bacteria, including C. minutissimum oral therapy indications widespread disease drugs erythromycin clarithromycin Complications Secondary bacterial infection