Skin nontumor
Infectious disorders
Corynebacteria
Editorial Board Member: Bethany R. Rohr, M.D.
Last author update: 5 August 2024
Last staff update: 5 August 2024
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PubMed Search: Corynebacteria
Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Etiology | Clinical features | Diagnosis | Laboratory | Prognostic factors | Case reports | Treatment | Clinical images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Sample pathology report | Differential diagnosis | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Liu L, Elsensohn AN. Corynebacteria. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skinnontumorcorynebacteria.html. Accessed December 22nd, 2024.
Definition / general
- Gram positive, catalase positive, non-spore forming bacilli or coccobacilli
- Commensal cutaneous organism but will cause diseases under certain circumstances
- Relevant cutaneous diseases: erythrasma, trichomycosis axillaris / trichobacteriosis, pitted keratolysis and cutaneous diphtheria
- Reference: J Clin Microbiol 2012;50:3152
Essential features
- Gram positive, non-spore forming bacilli or coccobacilli in stratum corneum
- Superficial cutaneous infections in humid environments
- Cutaneous diphtheria seen in pre-existing injuries or ulcers
Terminology
- Diphtheroids
- Corynebacterium flavescens, previously Corynebacterium tenuis
ICD coding
Epidemiology
- Erythrasma, pitted keratolysis and trichomycosis axillaris: typically in adults, especially in tropical or humid climates
- Cutaneous diphtherias: unvaccinated or individuals who travel to endemic areas
- Reference: Cureus 2020;12:e10733
Sites
- Erythrasma: caused by Corynebacterium minutissimum, intertriginous areas
- Pitted keratolysis: Corynebacteria species, plantar feet
- Trichomycosis axillaris: mostly caused by Corynebacterium flavescens; most common in axilla but pubic and scalp hairs can be involved (Cureus 2023;15:e45964)
- Cutaneous diphtheria: C. diphtheria and C. ulcerans; any cutaneous surface exposed to the organism
Etiology
- Erythrasma: superficial infection of the skin (organism in stratum corneum)
- Pitted keratolysis: superficial infection (organism in stratum corneum) with the breakdown of keratin and production of sulfur compounds by bacteria producing the pitting appearance and odor (Hoeger: Harper's Textbook of Pediatric Dermatology, 4th Edition, 2019)
- Trichomycosis: superficial infection of the hair shaft's soft keratin
- Cutaneous diphtheria: toxigenic or nontoxigenic strains colonize and infect pre-existing injured skin
Clinical features
- Erythrasma: red-brown macules coalescing into larger patches in intertriginous areas; coral-red fluorescence under Wood's lamp
- Pitted keratolysis: multiple discrete to coalescing circular erosions or pits on plantar surface, malodorous
- Trichomycosis: white-yellow sheaths and concretions adhering to the hair shaft, changes in hair texture or color, bromhidrosis or asymptomatic
- Cutaneous diphtheria: vesicle or pustule progressing to punched out lesions covered with a pseudomembrane or chronic nonhealing ulcers weeks to months in duration (J Clin Microbiol 2012;50:3152)
Diagnosis
- Erythrasma, pitted keratolysis, trichomycosis: clinical diagnosis
- Wood's lamp may be helpful
- Coral-red fluorescence under Wood's lamp in erythrasma
- Fluorescence of concretions on hair in trichomycosis
- Cutaneous diphtheria: based on laboratory diagnosis
- Reference: Cureus 2020;12:e10733
Laboratory
- Gram stain shows clusters of bacilli or coccobacilli
- Potassium hydroxide (KOH) prep with hair shaft concretions in trichomycosis axillaris
- Cutaneous diphtheria: wound swab culture, tissue culture, mass spectrometry, multiplex PCR analysis
- Reference: J Clin Microbiol 2012;50:3152
Prognostic factors
- Erythrasma, pitted keratolysis, trichomycosis: resolution with treatment
- Recurrence is common
Case reports
- 32 year old man with 3 years of worsening left forearm drainage, pain and deformity (Cureus 2023;15:e40854)
- 60 year old woman presented with slow healing right finger wound (Access Microbiol 2019;1:e000025)
- 78 year old man with melanonychia found to have subungual erythrasma (Skin Appendage Disord 2021;7:41)
- Elderly woman with type I diabetes mellitus presented with left leg injury with a thin membrane, fissures and secretion (Access Microbiol 2021;3:000284)
Treatment
- Erythrasma: topical or oral antibiotics (e.g., clindamycin and erythromycin)
- Pitted keratolysis: topical antibacterials (e.g., clindamycin and erythromycin) (Paediatr Child Health 2021;26:390)
- Trichomycosis axillaris: shaving of the hair and topical antibiotics
- Cutaneous diphtheria: oral penicillin or erythromycin; diptheria antitoxin if severe and worsening disease
Clinical images
Contributed by Rajendra Singh, M.D.
Erythrasma
Images hosted on other servers:
Cutaneous diphtheria
Coral-red fluorescence of erythrasma
Pitted keratolysis
Bacterial concretions in trichomycosis
KOH of trichomycosis
Microscopic (histologic) description
- Gram positive bacilli or coccobacilli in the superficial epidermis (stratum corneum)
Microscopic (histologic) images
Contributed by Rajendra Singh, M.D. and Bethany R. Rohr, M.D.
Pitted keratolysis
Erythrasma
Erythrasma
Positive stains
Sample pathology report
- Plantar feet, shave biopsy:
- Superficial bacterial infection (see comment)
- Comment: Multiple Gram positive coccobacilli are seen in the stratum corneum with minimal inflammatory response.
Differential diagnosis
- Candidiasis:
- Erosive, erythematous and well demarcated lesions; possible satellite pustulosis
- KOH preparation reveals pseudohyphae
- Pseudohyphae in the stratum corneum on histology
- Dermatophyte infection / tinea:
- Erythematous and scaly plaques
- KOH preparation reveals septate hyphae
- Septate hyphae in the stratum corneum on histology
- Tinea versicolor:
- Caused by the fungus Malassezia furfur
- Erythematous, hyperpigmented and hypopigmented lightly scaly lesions
- Hyphae and spores on KOH preparation
- Hyphae and clusters of spores in the stratum corneum
- Impetigo:
- Reference: Cureus 2020;12:e10733
Board review style question #1
A 14 year old boy presents with a malodorous eruption on his feet. What is the most likely diagnosis?
- Dyshidrotic eczema
- Erythrasma
- Pitted keratolysis
- Tinea pedis
Board review style answer #1
C. Pitted keratolysis. H&E shows superficial infection of stratum corneum with Gram positive coccobacilli. The history of clinical malodor is also suggestive of pitted keratolysis. Answer A is incorrect because spongiotic changes are not seen. Answer B is incorrect because clinically erythrasma tends to occur in intertriginous areas. Answer D is incorrect because tinea pedis would show hyphae, not bacteria, in the stratum corneum.
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Reference: Corynebacteria
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Reference: Corynebacteria
Board review style question #2
A 56 year old man with a history of type 2 diabetes, congestive heart failure and obesity presented with an asymptomatic rash on bilateral axillae for 1 month. The patient denied any prior treatment. On examination, erythematous plaques with mild scale were noted on bilateral axilla with a coral-red fluorescence under Wood's lamp. What is the expected histopathology?
- Gram positive coccobacilli in the stratum corneum
- Pseudohyphae with neutrophilic spongiosis
- Short hyphae and spores within the stratum corneum
- Spongiosis with perivascular lymphocytes
Board review style answer #2
A. Gram positive coccobacilli in the stratum corneum. Erythematous plaques in axillae with coral-red fluorescence are characteristic of erythrasma, which is caused by Gram positive coccobacilli in the stratum corneum. Answer C is incorrect because short hyphae and spores within the stratum corneum are diagnostic of Malassezia furfur and are highlighted with PAS or GMS staining. Answer B is incorrect because the presence of pseudohyphae with neutrophilic spongiosis would indicate candidiasis. Answer D is incorrect because spongiosis with perivascular lymphocytes describes eczema, which is a spongiotic process.
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Reference: Corynebacteria
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Reference: Corynebacteria
