Erythrasma

ICD-11

1C44

Synonyms

None.

Definition

Superficial infection with diphtheroid bacteria mostly affecting intertriginous areas.

Aetiology & Pathogenesis

Most infections are caused by Corynebacterium minutissimum.

Predisposing factors include obesity, diabetes, profuse sweating, occlusive clothing and a warm humid climate.

Signs & Symptoms

Sharply demarcated, red-brown, scaly patches, occasionally pruritic.

Localisation

Axillary, inguinal, toe clefts. Occasionally sub-mammary areas or extensive.

Classification

Interdigital erythrasma, intertriginous erythrasma, generalized/disciform erythrasma.

Laboratory & other workups

None.

Dermatopathology

Orthokeratosis with a minimal perivascular infiltrate in H&E staining. Gram staining shows positive rods and filaments in the stratum corneum.

Course

Chronic or recurs frequently.

Complications

Scratching with secondary infection with other microbes.

Diagnosis

Wood's light: coral red fluorescence (porphyrins from bacterial metabolism), culture (difficult).

Differential diagnosis

Tinea inguinalis and axillaris; contact dermatitis, pityriasis versicolor.

Prevention & Therapy

Topical treatment including antiseptics, ciclopirox, or imidazoles (clotrimazole, econazole), sometimes antibiotics (erythromycin). Severe cases can be treated with oral antibiotics (tetracycline, clarithromycin). Disappearance of red fluorescence indicates therapeutic success, hyperpigmentation may persist.

Avoid provoking factors (see above).

2.2.1 Erythrasma