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Erythrasma

BASICS

Erythrasma is a superficial bacterial infection of the skin folds caused by Corynebacterium minutissimum. It is often misdiagnosed as a fungal infection.

DESCRIPTION

  • C. minutissimum is a part of normal skin flora, but under moist, occluded conditions, the diphtheroid bacteria will cause well-defined, reddish brown plaques in intertriginous areas such as the inguinal, intergluteal, interdigital, and inframammary folds.
  • Concomitant fungal infections, predominately Candida, are seen in ~30% of patients (1).
  • In the immunocompetent patient, erythrasma may be a minor chronic skin disorder; however, in the immunocompromised population, especially HIV patients, C. minutissimum can progress to severe cellulitis, abscess, or bacteremia (2).

EPIDEMIOLOGY

Incidence

Incidence is reported ~4%. Higher incidence in immunocompromised, predisposed, and elderly populations but has been reported in all ages. Both sexes appear equally affected (3).

Prevalence

Erythrasma appears more in subtropical and tropical areas.

ETIOLOGY AND PATHOPHYSIOLOGY

C. minutissimum is a normal skin bacteria; however, under warm, humid, occlusive conditions, this bacteria invades the stratum corneum layer of epidermis causing it to thicken and scale. These diphtheroids produce porphyrin, which causes bright coral-red fluorescence of the skin under Wood light.

RISK FACTORS

  • Obesity
  • Diabetes
  • Occlusive clothing/shoes
  • Hyperhidrosis
  • Immunocompromised state
  • Advanced age
  • Living in a subtropical or tropical region

GENERAL PREVENTION

  • Nonocclusive clothing and footwear
  • Good hygiene
  • Weight loss
  • Good blood sugar control
  • Avoiding constant skin friction

COMMONLY ASSOCIATED CONDITIONS

Coexisting fungal infections

DIAGNOSIS

HISTORY

  • Normally, erythrasma is asymptomatic; however, it may present with pruritus (2).
  • Reddish/brown discolored irregular patches
  • Affects intertriginous areas, interdigital areas
  • Consider when no improvement after antifungal therapy used for "fungal infection" (1).

PHYSICAL EXAM

Skin lesions present initially as red patches that are sharply demarcated, with irregular borders, that later may become brown/tan color. In toe web spaces, can appear fissuring, macerated, and scaling (4). May be mistaken for tinea pedis

DIFFERENTIAL DIAGNOSIS

  • Psoriasis
  • Dermatophytosis
  • Acanthosis nigricans
  • Intertriginous candidiasis
  • Pitted keratolysis
  • Tinea versicolor

DIAGNOSTIC TESTS & INTERPRETATION

Wood lamp exam (UV light)-skin will fluoresce a coral red color, whereas tinea cruris or cutaneous candidal infections won't fluoresce (5).

Initial Tests (lab, imaging)

  • Obtain skin scrapings, if possible, to view under microscope; consider potassium hydroxide (KOH) test to exclude dermatophytoses (2).
  • Visualize skin lesions under Wood lamp, although not always reliable (2).
  • Gram stain may show gram-positive, rod-shaped organisms.

Follow-Up Tests & Special Considerations

Culture

Test Interpretation

  • Wood lamp will show a coral red-colored fluorescence due to the presence of porphyrins.
  • Under microscopic exam, rod-like bacteria are seen in the stratum corneum layer of skin (2).

TREATMENT

  • Erythromycin is treatment of choice, and a recent systematic review showed "convincing evidence" to recommend erythromycin; however, no evidence-based studies have clarified the best therapeutic options (2)[A],(6)[B].
  • Red light photodynamic therapy may also be effective. One recent study showed ~23% of patients had complete recovery from lesions, whereas others had some reduction in extent of their lesions (7)[C].

GENERAL MEASURES

  • Athletes/military recruits should be treated for 48 to 72 hours prior to returning to contact situations (1)[C].
  • Asymptomatic individuals, especially athletes, should be treated (1)[C].

MEDICATION

First Line

  • Erythromycin base 250 mg PO QID for 14 days; systemic therapy preferred for widespread or multisite disease (1,2)[C]
  • Topical erythromycin 2% BID 7 to 10 days (1)[C]
  • Topical clindamycin 2% TID for 7 to 14 days (1)[C]

ADDITIONAL THERAPIES

  • Clarithromycin 1 g PO single dose (1)[C]
  • Tetracycline 250 mg PO QID for 7 to 14 days (1)[C]
  • Photodynamic therapy with red light (7)[C]

ISSUES FOR REFERRAL

In case of outpatient therapeutic failure or contraindication of systemic drugs, or immunocompromised, patient should be referred to specialists and may require inpatient therapy in the latter case due to possible complications.

ONGOING CARE

PATIENT EDUCATION

Patients should be counseled to keep affected areas clean and dry and to avoid occlusive clothing and footwear.

PROGNOSIS

Good

COMPLICATIONS

Immunocompromised patients with erythrasma need to be cautious of septicemia, and patients with valvular heart disease or postsurgical wounds need to monitor for possible infective endocarditis and infection, respectively.

REFERENCES

11 Sedgwick PE, Dexter WW, Smith CT. Bacterial dermatoses in sports. Clin Sports Med. 2007;26(3):383-396.22 Blaise G, Nikkels AF, Hermanns-L Ş T, et al. Corynebacterium-associated skin infections. Int J Dermatol. 2008;47(9):884-890.33 Husain Z, Cohen PJ, Schwartz RA, et al. Flexural and extensoral eruptions in dermatologic disease. Clin Dermatol. 2011;29(2):195-204.44 Morales-Trujillo ML, Arenas R, Arroyo S. Interdigital erythrasma: clinical, epidemiologic, and microbiologic findings [in Spanish]. Actas Dermosifiliogr. 2008;99(6):469-473.55 Hainer BL. Dermatophyte infections. Am Fam Physician. 2003;67(1):101-108.66 Eekhof JA, Neven AK, Gransjean SP, et al. Minor derm ailments: how good is the evidence for common treatments? J Fam Pract. 2009;58(9):E2.77 Darras-Vercambre S, Carpentier O, Vincent P, et al. Photodynamic action of red light for treatment of erythrasma: preliminary results. Photodermatol Photoimmunol Photomed. 2006;22(3):153-156.

ADDITIONAL READING

  • Janniger CK, Schwartz RA, Szepietowski JC, et al. Intertrigo and common secondary skin infections. Am Fam Physician. 2005;72(5):833-838.
  • Kalra MG, Higgins KE, Kinney BS. Intertrigo and secondary skin infections. Am Fam Physician. 2014;89(7):569-573.

CODES

ICD10

L08.1 Erythrasma

ICD9

039.0 Cutaneous actinomycotic infection

SNOMED

Erythrasma (disorder)

CLINICAL PEARLS

Erythrasma is a bacterial infection of the skin folds, often misdiagnosed as a fungal infection.