Practice Essentials
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.
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 lamp 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.
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:
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Excessive sweating/hyperhidrosis
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Delicate cutaneous barrier
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Obesity
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Diabetes mellitus
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Warm climate
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Poor hygiene
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Advanced age
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Other immunocompromised states
Epidemiology
United States and international statistics
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.
Prognosis
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]
Patient Education
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.
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Lichenification and hyperpigmentation are common. Skin occasionally appears wrinkled, with scales. KOH test results are negative. Image from Michael Bryan, MD.
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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 recently, pigment may be washed away. In suspicious cases, repeat examination on following day may be necessary. Image from Michael Bryan, MD.
