Erythrasma is a chronic superficial infection of the intertriginous areas of the skin.[1] The incriminated organism is Corynebacterium minutissimum, which usually is present as a normal human skin inhabitant. In 1996, Corynebacterium afermentans was reported in one case.[2] In a 2011 report, two colonies of Corynebacterium aurimucosum and Microbacterium oxydans were isolated from the interdigital web of the left foot in a 78-year-old woman, indicating that other species of microorganisms may be capable of causing this condition.[3]
The typical appearance of erythrasma is well-demarcated, brown-red macular patches. The skin appears wrinkled, with fine scales. (See Presentation.) Infection commonly is located on the inner thighs, crural region, scrotum, and toe webs; the axillae, submammary area, periumbilical region, and intergluteal folds are less commonly involved. Because erythrasma may be associated with other corynebacterial skin infections, all body folds and feet should be screened.
Infection may be treated with topical agents, oral agents, or both. First-line therapy has generally involved topical erythromycin or clindamycin or cream containing fusidic acid (not available in the United States) or miconazole. (See Treatment.) Second-line therapy may involve oral erythromycin or single-dose clarithromycin or amoxicillin-clavulanate for systemic treatment. Although C minutissimum is generally susceptible to penicillins, first-generation cephalosporins, erythromycin, clindamycin, ciprofloxacin, tetracycline, and vancomycin, multiresistant strains have been isolated.
Corynebacteria invade the upper third of the stratum corneum; under favorable conditions such as heat and humidity, these organisms proliferate. The stratum corneum is thickened. The organisms that cause erythrasma are seen in the intercellular spaces as well as within cells, dissolving keratin fibrils. The coral-red fluorescence of scales seen under Wood lamp light is secondary to the production of porphyrin by these diphtheroids.
C minutissimum, a member of the normal skin flora, is the causative agent of erythrasma. The bacterium is a lipophilic, gram-positive, non-spore-forming, aerobic, and catalase-positive diphtheroid. C minutissimum ferments glucose, dextrose, sucrose, maltose, and mannitol.
Whole-genome sequencing of C minutissimum has been carried out with the goal of improved understanding of the multiantibiotic resistance that has been observed and its virulence factors, specifically in immunocompromised hosts. This will make it possible to identify the genes contributing to antibiotic resistance and thus to develop better-designed treatment options for these special cases.[4]
Predisposing factors for erythrasma include the following:
The incidence of erythrasma is reported to be around 4%. This infection is observed all over the world; the widespread form is found more frequently in the subtropical and tropical areas than in other parts of the world. Erythrasma occurs less often in children and tends to be more prevalent among college students in dormitories, soldiers in barracks, and senior adults in nursing facilities.
In a study conducted in Turkey, the rate of erythrasma was found to be 46.7% among 122 patients with interdigital foot lesions.[5]
In a cross-sectional study of 80 patients with confirmed superficial cutaneous intertriginous infections in Tehran, Iran, erythrasma was the second most common infection after dermatophytosis[6] ; it accounted for 35% of the cases. The toe-web spaces were the most common sites, followed by the groin and axillary vaults.
The occurrence of erythrasma on the palm of one patient was described in a report by Rao et al.[7] This appears to be extremely rare, if not unique.
Age-, sex-, and race-related demographics
The incidence of erythrasma increases with age; however, no age group is immune to the disease. Erythrasma has been reported in children as young as 1 year.
Males and females are equally affected by erythrasma; however, the crural form is more common in men. A 2008 study found that interdigital erythrasma was more common in women (83% of 24 patients).[8] A later study conducted in India confirmed the absence of sex predilection and observed that it was more commonly detected in patients with a body mass index (BMI) higher than 23 kg/m2 (62.5%) and in those with diabetes (50%).[9]
The incidence of erythrasma is higher in Black patients.
The prognosis for erythrasma is excellent; however, the condition tends to recur if the predisposing factors are not eliminated.
Although erythrasma is usually a benign condition, it may become widespread and invasive in predisposed and immunocompromised individuals; this is very rare in immunocompetent hosts. In such individuals, this organism has caused infections other than erythrasma. Reports have cited abscess formation (n= 3),[10] intravascular catheter–related infections (n = 2),[11] primary bacteremia (n = 3), peritoneal catheter–related infections (n = 2),[11, 12] endocarditis (n = 2),[13, 14] pyelonephritis (n = 2),[15, 16] cellulitis (n = 1),[17] endophthalmitis (n = 1),[18] arteriovenous fistula infection (n = 1), cutaneous granuloma (n = 1),[19] and meningitis (n = 1).[20]
In 2014, Shin et al reported the first known case of postoperative intra-abdominal infection caused by C minutissimum in an immunocompetent adult host; the infection was successfully treated with intravenous amoxicillin-sulbactam.[21]
Any patient with erythrasma should be advised to change his or her lifestyle by engaging in exercise and, if relevant, weight loss (because obesity is a major risk factor). In addition, personal hygiene and environment acclimatization should be underscored. Wearing cotton garments rather than synthetic fabrics is yet another consideration for keeping the sites of predilection dry. Finally, eating healthily and limiting intake of sugary foods (especially for people with diabetes) will help minimize the risk for this disease.
The dark discoloration associated with erythrasma is usually limited to body folds that are naturally moist and occluded. Infection commonly is asymptomatic, but it can be pruritic. The duration of erythrasma ranges from months to years. Widespread involvement of trunk and limbs is possible.
Immunosuppressed patients with erythrasma and an increased risk of complications are of special concern. Any possible concomitant infection must be evaluated and treated. In cases of recurrent erythrasma, diabetes should be suspected. Risk factors should be addressed and modified to the extent possible.
The typical appearance of erythrasma is well-demarcated, brown-red macular patches. The skin has a wrinkled appearance with fine scales (see the image below).
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Lichenification and hyperpigmentation are common. Skin occasionally appears wrinkled, with scales. KOH test results are negative. Image from Michael B....
Infection commonly is located on the inner thighs, crural region, scrotum, and toe webs. Toe web lesions appear as maceration, with the fourth interdigital space most frequently affected.[8] The axillae, submammary area, periumbilical region, and intergluteal folds are less commonly involved in erythrasma. A few cases of erythrasma of the vulva have been reported.[22]
Given the association of erythrasma with other corynebacterial skin infections (eg, pitted keratolysis and trichomycosis axillaris), it is important that all body folds and feet be screened. Blaise et al investigated this association in 53 patients with pitted keratolysis who had skin signs of other corynebacterial infections.[23] Erythrasma was encountered in two of the 53, whereas trichobacteriosis was noted in four. One patient presented with all three conditions present simultaneously.
A study (N = 30) by Janeczek et al found a high prevalence of erythrasma in patients with inverse psoriasis.[24]
Wood lamp examination of erythrasma lesions reveals coral-red fluorescence of lesions (see the image below). Results may be negative if the patient bathed before presentation.[31] The cause of this color fluorescence has been attributed to excess coproporphyrin III synthesis by the corynebacteria; the porphyrin accumulates in cutaneous tissue and emits a coral-red fluorescence when exposed to light from a Wood lamp.[32] If a Wood lamp is not available, a smartphone app that simulates ultraviolet (UV) light may be considered as an alternative.[33]
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Under Wood lamp examination, porphyrins produced by bacteria fluoresce with coral pink color. Small focus is visible on photo. If patient has bathed r....
In culture media composed of 20% fetal bovine serum, 2% agar, 78% tissue culture medium #199, and 0.05% tris, the organisms grow as nonhemolytic 1- to 1.5-mm smooth colonies. Methylene blue stain may be used to highlight both the fungal spores of pityriasis versicolor and the curved or club-shaped bacterial rods of C minutissimum, in case the two organisms are coexisting.[26]
In a study comparing the diagnostic yield of Wood lamp examination with that of Gram staining, it was found that 9% of patients were positive on the former and 15.6% were positive on the latter.[30] Concurrent use of Wood lamp examination and Gram staining resulted in a higher yield of positive findings (22.1%).
Erythrasma may be treated with topical agents, oral agents, or both. First-line therapy consists of topical erythromycin or clindamycin or fusidic acid or miconazole cream. In the United States, however, fusidic acid is not available; consequently, topical treatment with the other agents mentioned is the standard of care.
A 2017 report by Greywal et al described the use of mupirocin 2% ointment monotherapy on a series of nine male patients twice daily for 2-4 weeks, with complete resolution of their signs and symptoms.[34] Another topical treatment that has been tried is ozonated olive oil every 12 hours for 10 days, which yielded a 100% cure rate in a report by Ramírez-Hobak et al.[35]
Oral erythromycin is usually effective and is a good second-line therapy, as is single-dose clarithromycin[36] or amoxicillin-clavulanate, for systemic treatment.[37]
C minutissimum is generally susceptible to penicillins, first-generation cephalosporins, erythromycin, clindamycin, ciprofloxacin, tetracycline, and vancomycin. However, multiresistant strains have been isolated.[38, 39, 40] In a susceptibility study (N = 40) by Turk et al, several antibiotics were tested in patients with erythrasma, including penicillin G, ampicillin, cefaclor, amoxicillin-clavulanate, ampicillin-sulbactam, tetracycline, erythromycin, ofloxacin, fusidic acid, levofloxacin, and azithromycin.[37] Significant resistance to erythromycin, azithromycin, penicillin, and ampicillin was noted. Significant susceptibility to amoxicillin-clavulanate, cefaclor, and fusidic acid was found.
In a large double-blind placebo-controlled randomized trial (N = 151), patients older than 18 years were randomized into five groups and given either erythromycin, single-dose clarithromycin, topical fusidic acid, placebo cream, or placebo tablets.[41] Fusidic acid cream was significantly more effective than other therapies. Additionally, the clarithromycin group did better at 48 hours than the erythromycin group did; however, there was no statistical difference on day 7 and day 14.
In one report (N = 13), photodynamic therapy using red light (broadband, peak at 635 nm) cleared erythrasma in 23% of cases and improved erythrasma in the remaining cases[42] ; however, such therapy is not the treatment of choice.
Clinical Context:
Erythromycin is the drug of choice. It inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest. In children, age, weight, and severity of infection determine the proper dosage. When twice-daily dosing is desired, half the total daily dose may be taken every 12 hours. For more severe infections, double the dose.
Clinical Context:
Erythromycin inhibits protein synthesis in susceptible organisms by reversibly binding to 50 S ribosomal subunits, thereby inhibiting translocation of aminoacyl transfer-RNA and inhibiting polypeptide synthesis.
Clinical Context:
Clarithromycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
Clinical Context:
Clindamycin has a bacteriostatic effect; it interferes with bacterial protein synthesis similarly to erythromycin and chloramphenicol by binding to the 50S subunit of bacterial ribosomes.
Clinical Context:
Clindamycin is an antibacterial agent that binds to the 50S ribosomal subunits of susceptible bacteria and prevents elongation of peptide chains by interfering with peptidyl transfer, thereby suppressing protein synthesis.
Clinical Context:
Tetracycline inhibits cell growth by inhibiting mRNA translation. It binds to the 16S part of 30S ribosomal subunits and prevents amino-acyl tRNA from binding to the A site of ribosomes. Binding is reversible in nature.
Clinical Context:
Miconazole damages the fungal cell wall membrane by inhibiting the biosynthesis of ergosterol. Membrane permeability is increased, causing nutrients to leak out and resulting in fungal cell death. Lotion is preferred in intertriginous areas. If cream is used, apply sparingly to avoid maceration effects. Use 2% cream.
What is erythrasma?What is the pathophysiology of erythrasma?What is the causative agent of erythrasma?What are the predisposing factors for erythrasma?What is the prevalence of erythrasma?What are the racial predilections of erythrasma?How does the prevalence of erythrasma vary by sex?How does the incidence of erythrasma vary by age?What is the prognosis of erythrasma?What is the prognosis of erythrasma in predisposed and immunocompromised individuals?What should patients be told about erythrasma?Which patient history is characteristic of erythrasma?What is the typical appearance of erythrasma?Which areas should be included in the physical exam of erythrasma?What are the possible complications of erythrasma?Which conditions may coexist with erythrasma?What is the role of KOH exam in the evaluation of erythrasma?What are the differential diagnoses for Erythrasma?Which findings on Wood Light exam indicate erythrasma?What is the role of culture and staining in the workup of erythrasma?How accurate are Wood lamp and gram staining for the identification of erythrasma?Which histologic findings are characteristics of erythrasma?What are the treatment options for erythrasma?What is the role of photodynamic therapy in the treatment of erythrasma?What are the goals of drug treatment for erythrasma?Which medications in the drug class Antifungals are used in the treatment of Erythrasma?Which medications in the drug class Antibiotics are used in the treatment of Erythrasma?
Abdul-Ghani Kibbi, MD, FACP, Professor and Chair, Department of Dermatology, American University of Beirut Medical Center, Lebanon
Disclosure: Nothing to disclose.
Specialty Editors
Richard P Vinson, MD, Assistant Clinical Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine; Consulting Staff, Mountain View Dermatology, PA
Disclosure: Nothing to disclose.
Chief Editor
William D James, MD, Emeritus Professor, Department of Dermatology, University of Pennsylvania School of Medicine
Disclosure: Received income in an amount equal to or greater than $250 from: Elsevier<br/>Served as a speaker for various universities, dermatology societies, and dermatology departments.
Additional Contributors
Fady G Haddad, MD, Specialist Dermatologist, Dubai Healthcare City, UAE
Disclosure: Nothing to disclose.
Maria S Bou Sleiman, MD, Resident Physician, Department of Dermatology, American University of Beirut Medical Center
Disclosure: Nothing to disclose.
Robin Travers, MD, Assistant Professor of Medicine (Dermatology), Dartmouth University School of Medicine; Staff Dermatologist, New England Baptist Hospital; Private Practice, SkinCare Physicians
Disclosure: Nothing to disclose.
Ruba Faik Bahhady, MD, Senior Specialist, Department of Dermatology, American University of Beirut Medical Center
Disclosure: Nothing to disclose.
Acknowledgements
Zenus Saleh, MD Staff Physician, Department of Dermatology, American University of Beirut Medical Center
Zenus Saleh, MD is a member of the following medical societies: Alpha Omega Alpha
Lichenification and hyperpigmentation are common. Skin occasionally appears wrinkled, with scales. KOH test results are negative. Image from Michael Bryan, MD.
Under Wood lamp examination, porphyrins produced by bacteria fluoresce with coral pink color. Small focus is visible on photo. If patient has bathed recently, pigment may be washed away. In suspicious cases, repeat examination on following day may be necessary. Image from Michael Bryan, MD.
Lichenification and hyperpigmentation are common. Skin occasionally appears wrinkled, with scales. KOH test results are negative. Image from Michael Bryan, MD.
Under Wood lamp examination, porphyrins produced by bacteria fluoresce with coral pink color. Small focus is visible on photo. If patient has bathed recently, pigment may be washed away. In suspicious cases, repeat examination on following day may be necessary. Image from Michael Bryan, MD.
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