Extensive and Bullous Impetigo
A 9-year-old girl has a 6-day history of spreading skin lesions. Examination shows more than 15 erosions covered by honey-coloured crusts plus several flaccid bullae over the trunk, both arms and the chin, involving roughly 8% of body surface area. Temperature is 37.9 °C, with tender cervical lymph nodes, no mucosal involvement and no skin sloughing on gentle pressure. What is the most appropriate treatment?
- A.Topical permethrin 5% cream
- B.Topical mupirocin ointment alone
- C.Oral fluconazole for 7 days
- D.Oral cephalexin for 7 daysCorrect
Explanation
Impetigo is treated topically when disease is limited, but oral antibiotics are indicated when lesions are numerous or widespread, when bullae are present, when there are systemic features such as fever and lymphadenopathy, or during outbreaks; all of these apply here. Bullous impetigo is caused by Staphylococcus aureus strains producing exfoliative toxin A, which cleaves desmoglein 1 in the superficial epidermis and creates flaccid, easily ruptured bullae that leave a collarette of scale. First-line oral therapy therefore targets S. aureus and Streptococcus pyogenes with a first-generation cephalosporin such as cephalexin, or cloxacillin or amoxicillin-clavulanate; clindamycin, doxycycline (over 8 years) or trimethoprim-sulfamethoxazole are used when methicillin-resistant S. aureus is suspected. Topical mupirocin alone is inadequate for this burden of disease and would not treat the systemic component. Fluconazole targets Candida and dermatophytes, which cause satellite pustules in moist flexures or annular scaly plaques rather than honey crusts. Permethrin treats scabies, which presents with intensely itchy burrows in the web spaces, wrists and axillae. The key differential to exclude is staphylococcal scalded skin syndrome, in which the same toxin acts systemically to produce diffuse tender erythema, a positive Nikolsky sign and perioral radial fissuring, and which requires intravenous antistaphylococcal therapy; the absence of skin sloughing here argues against it.
Why each option
- A.
- Permethrin treats scabies, which causes itchy burrows rather than honey-crusted erosions and flaccid bullae.
- B.
- Topical therapy is appropriate only for a few localized lesions and cannot control disease covering 8% of body surface with systemic features.
- C.
- Fluconazole is an antifungal and has no activity against Staphylococcus aureus or Streptococcus pyogenes.
- D.
- Correct. Widespread bullous impetigo with fever and lymphadenopathy requires systemic antistaphylococcal therapy such as cephalexin.
Reference: IDSA Skin and Soft Tissue Infection Guideline; Nelson Textbook of Pediatrics, 22nd ed., 2024
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