Erythrasma
Definition
Erythrasma is a superficial bacterial skin infection typically found in skin folds (e.g. axillae, groin, interdigital spaces). It presents as hyperpigmented, thin patches that may be mistaken for fungal infections. Under a Wood’s lamp, erythrasma demonstrates a characteristic coral-pink fluorescence.
Aetiology & Causes
Caused by Corynebacterium minutissimum (Gram-positive, non-spore-forming bacillus).
Commonly misdiagnosed as tinea or candidal infection due to similar rash patterns.
Risk Factors
Warm, humid climates
Excessive sweating (hyperhidrosis)
Skin of colour (hyperpigmentation more evident)
Diabetes, obesity, poor hygiene
Advanced age (compromised skin barrier)
Clinical Features
Well-demarcated pinkish-brown patches with fine scaling; can sometimes have superficial fissures.
Usually mildly pruritic or asymptomatic, though some patients report mild itch or discomfort.
Common sites:
May co-exist with fungal infections (e.g. tinea).
Diagnosis
Wood’s Lamp Examination: Coral-pink fluorescence due to porphyrin production by C. minutissimum.
Microscopy: Gram stain or methylene blue stain can identify C. minutissimum.
Differential: Tinea cruris, intertrigo (candida), inverse psoriasis.
Further Assessments: Check for underlying risk factors like diabetes if recurrent or extensive.
Management
Topical Treatment (First-Line)
Fusidic Acid 2% Ointment BD for 2 weeks
Whitfield’s Ointment (benzoic acid and salicylic acid) can also be used
Alternatives: Topical clindamycin or erythromycin if fusidic acid is unavailable
Oral Treatment (If Extensive or Recurrent)
Clarithromycin 1 g stat (single dose)
Erythromycin or Tetracycline (doxycycline) for 7–14 days if needed
Oral therapy is particularly beneficial in widespread disease or if topical therapy fails
Other Options
Photodynamic Therapy (red light): Reported in some cases, though not routinely used in Australian practice
Ensure adequate dryness of skin folds; consider antifungal if co-existing tinea
Prevention
Antibacterial soaps or washes to reduce skin colonisation
Keep skin folds dry (use absorptive powders, wear loose clothing)
Repeat treatment or maintenance topical therapy if recurring
Address underlying factors:
Notes
Erythrasma can recur, especially if risk factors (e.g. sweating, obesity, diabetes) are not addressed.
Consider checking for co-infection with dermatophytes (tinea) as it may coexist in similar sites.
Some guidelines suggest combining topical antibacterial with antifungal if diagnosis is uncertain.
