Background
Erythrasma is a chronic superficial infection of the intertriginous areas of the skin. 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.[1]
In a more recent study, 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 responsible for this condition.[2]
Pathophysiology
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 light is secondary to the production of porphyrin by these diphtheroids.
Etiology
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.
Predisposing factors for erythrasma include the following:
Excessive sweating/hyperhidrosis
Delicate cutaneous barrier
Obesity
Diabetes mellitus
Warm climate
Poor hygiene
Advanced age
Other immunocompromised states
Epidemiology
Frequency
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.[3]
In a study conducted in Turkey, the rate of erythrasma was found to be 46.7% among 122 patients with interdigital foot lesions.[4]
Race
The incidence of erythrasma is higher in black patients.
Sex
Both sexes are equally affected by erythrasma; however, the crural form of erythrasma is more common in men. A 2008 study found that interdigital erythrasma was more common in women (83% of 24 patients).[5]
Age
The incidence of erythrasma increases with age, but no age group is immune to the disease. The youngest patient reported to have erythrasma is a 1-year-old infant.
Prognosis
The prognosis for erythrasma is excellent; however, the condition tends to recur if the predisposing factors are not eliminated.
Erythrasma is usually a benign condition. However, 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. These include abscess formation (3 cases),[6] intravascular catheter–related infections (2 cases),[7] primary bacteremia (3 cases), peritoneal catheter–related infections (2 cases),[7, 8] endocarditis (2 cases),[9, 10] pyelonephritis (2 cases),[11, 12] cellulitis (1 case),[13] endophthalmitis (1 case),[14] arteriovenous fistula infection (1 case), cutaneous granuloma (1 case),[15] and meningitis (1 case).[16]
The first case of postoperative intraabdominal infection caused by Corynebacterium minutissimum in an immunocompetent adult host was reported and has been successfully treated with intravenous amoxicillin/sulbactam.[17]
Patient Education
Patients with erythrasma should be instructed to keep the area dry.
History
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 the risk of complications are of special concern. Evaluate and treat possible concomitant infection. Suspect diabetes in recurrent erythrasma. Address and modify risk factors for successful treatment.
Physical Examination
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).
View Image | Lichenification and hyperpigmentation are common. The skin occasionally has a wrinkled appearance with scales. KOH test results are negative. Courtesy.... |
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 in erythrasma. Toe web lesions appear as maceration, with the fourth interdigital space most frequently affected.[5]
Owing to the association of erythrasma with other corynebacterial skin infections such as pitted keratolysis and trichomycosis axillaris, all body folds and feet should be screened. This association has been investigated in 53 patients with pitted keratolysis who had skin signs of other corynebacterial infections. Erythrasma was encountered in 2 of 53 of this cohort in male patients, whereas trichobacteriosis was noted in 4 of 53. One patient presented simultaneously with all the three conditions.[18]
Complications
Note the following possible complications:
Fatal septicemia in immunocompromised patients with erythrasma
Infective endocarditis in valvular heart disease patients with erythrasma
Postsurgical wound infection in erythrasma patients
Laboratory Studies
Wood light examination of erythrasma lesions reveals coral-red fluorescence of lesions. Results may be negative if the patient bathed prior to presentation.[26] Note the image below. The cause of this color fluorescence has been attributed to excess coproporphyrin III synthesis by these organisms, which accumulates in cutaneous tissue and emits a coral-red fluorescence when exposed to a Wood light.[27]
View Image | Under Wood lamp examination, the porphyrins produced by the bacteria fluoresce with a coral pink color. A small focus is visible on this photo. If the.... |
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, the causative agent of erythrasma, in case both organisms coexist.[20]
Comparing the diagnostic yield between Wood lamp examination and Gram stain, it was found that 9% of patients were positive on the former and 15.6% were positive on the latter. Using both Wood lamp examination and Gram staining concurrently resulted in a higher yield of 22.1% for positive patients.[25]
Histologic Findings
The diphtheroid bacteria that cause erythrasma are present in the horny layer as rods and filaments.[28]
Medical Care
Infection may be treated with topical and/or oral agents. First-line therapy is topical erythromycin or clindamycin, or fusidic acid cream or miconazole cream. However, fusidic acid is not available in the United States, so topical treatment with the other agents mentioned is the standard of care in the United States. Oral erythromycin is usually effective and is a good second-line therapy, as is single-dose clarithromycin or amoxicillin-clavulanate, for systemic treatment.[29] Therapy must be comprehensive and cover all likely pathogens in the context of this clinical setting.
C minutissimum is generally susceptible to penicillins, first-generation cephalosporins, erythromycin, clindamycin, ciprofloxacin, tetracycline, and vancomycin. However, multiresistant strains have been isolated.[30, 31, 32, 33] In a susceptibility study of 40 patients, several antibiotics were tested, including penicillin G, ampicillin, cefaclor, amoxicillin-clavulanate, ampicillin-sulbactam, tetracycline, erythromycin, ofloxacin, fusidic acid, levofloxacin, and azithromycin. The study revealed statistically significant resistance to erythromycin, azithromycin, penicillin, and ampicillin. Significant susceptibility was statistically found to amoxicillin-clavulanate, cefaclor, and fusidic acid.[29]
In a large double-blind, placebo-controlled, randomized trial, 151 patients older than 18 years were randomized into five groups and were given either erythromycin, single-dose clarithromycin, topical fusidic acid, placebo cream, or placebo tablets. Fusidic acid cream was significantly more effective than other therapies. Additionally, the group that received clarithromycin did better at 48 hours than did the group that received erythromycin. However, there was no statistical difference on day 7 and day 14.[34]
Photodynamic therapy using red light (broadband, peak at 635 nm) has been reported to clear erythrasma in 23% of 13 patients and to improve erythrasma in the remaining patients; however, it is not the treatment of choice.
Medication Summary
The goals of pharmacotherapy for erythrasma are to reduce morbidity, eradicate the infection, and prevent complications.
Erythromycin (E.E.S., E-Mycin, Ery-Tab)
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.
Clarithromycin (Biaxin)
Clinical Context:
Clarithromycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
Miconazole topical (Femazole, Lotrimin, Monistat)
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.
Clindamycin (Cleocin)
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.
Tetracycline (Achromycin)
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.
Class Summary
Antibacterial and/or antifungal agents are used to eradicate C minutissimum and possible concomitant infection.
Author
Abdul-Ghani Kibbi, MD, Professor and Chair, Department of Dermatology, American University of Beirut Medical Center, Lebanon
Disclosure: Nothing to disclose.
Coauthor(s)
Maria S Bou Sleiman, MD, Resident Physician, Department of Dermatology, American University of Beirut Medical Center
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, Paul R Gross Professor of Dermatology, Vice-Chairman, Residency Program Director, Department of Dermatology, University of Pennsylvania School of Medicine
Disclosure: Received income in an amount equal to or greater than $250 from: Elsevier; WebMD.
Additional Contributors
Fady G Haddad, MD, Specialist Dermatologist, Dubai Healthcare City, UAE and AR Shamma 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
Disclosure: Nothing to disclose.
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