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.
Whole-genome sequencing of C minutissimum has been reported to better understand the multiantibiotic resistance that has been observed and its virulence factors specifically in immunocompromised hosts. The will make it possible to identify the genes contributing to antibiotic resistance and to better design treatment options in these special cases. [3]
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
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. [4] .The infection 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. Erythrasma incidence may increase with age.
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 has been reported and appears to be unique and rare. [7]
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). [8]
A more recent 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 of greater than 23 kg/m2 (62.5%) and in those with diabetes (50%). [9]
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), [10] intravascular catheter–related infections (2 cases), [11] primary bacteremia (3 cases), peritoneal catheter–related infections (2 cases), [11, 12] endocarditis (2 cases), [13, 14] pyelonephritis (2 cases), [15, 16] cellulitis (1 case), [17] endophthalmitis (1 case), [18] arteriovenous fistula infection (1 case), cutaneous granuloma (1 case), [19] and meningitis (1 case). [20]
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. [21]
Patient Education
Any patient with erythrasma should be advised to change his or her life style by engaging in exercise and 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 to keep the sites of predilection dry. Finally, eating healthy and limiting the intake of sugary foods, especially people with diabetes, is an adjuvant to minimize the risk for this disease. [22]
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Lichenification and hyperpigmentation are common. The skin occasionally has a wrinkled appearance with scales. KOH test results are negative. Courtesy of Michael Bryan, MD.
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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 patient recently has bathed, the pigment may be washed away. In suspicious cases, a repeat examination the following day may be necessary. Courtesy of Michael Bryan, MD.
