Definition
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Impetigo: superficial bacterial skin infection, commonly affecting children.
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Characterized by pustules, vesicles, or honey-colored crusts, usually on the face or extremities.
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Highly contagious via direct contact or fomites.
Epidemiology & Risk Factors
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Most common in children aged 2–5 years, but can occur at any age.
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More common in hot, humid climates.
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Risk factors:
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Minor skin trauma (scratches, insect bites)
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Pre-existing eczema or dermatitis
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Crowded living conditions
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Poor hygiene
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Etiology
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Staphylococcus aureus – most common cause
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Streptococcus pyogenes (Group A Streptococcus)
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Mixed infections possible
Clinical Features
| Feature | Description | High-Yield Points |
|---|---|---|
| Lesion type | Vesicles, pustules, or bullae; ruptures to form honey-colored crusts | Bullous vs non-bullous forms |
| Distribution | Face (perioral, around nose), extremities | Usually exposed areas |
| Symptoms | Mild pruritus | Pain uncommon unless secondary infection |
| Systemic features | Usually none | Fever possible in severe cases or bullous impetigo |
Types:
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Non-bullous impetigo: small vesicles → honey-colored crusts; most common
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Bullous impetigo: larger flaccid bullae; usually S. aureus (exfoliative toxin)
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Ecthyma: deeper ulceration, often on lower extremities
Differential Diagnosis
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Folliculitis – lesions centered on hair follicles
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Herpes simplex – grouped vesicles on erythematous base, often painful
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Contact dermatitis – diffuse erythema, no pustules or crust
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Scabies – burrows, intense nocturnal pruritus
Investigations
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Usually clinical diagnosis.
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Swab and culture if:
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Severe, recurrent, or non-responding infection
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Suspected MRSA
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Management
General Measures
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Hygiene: wash lesions, avoid sharing towels, keep fingernails short
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Cover lesions to reduce spread
Topical Therapy
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Mild, localized cases: mupirocin or fusidic acid cream
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Apply 2–3 times daily for 5–10 days
Systemic Therapy
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Extensive or widespread disease: oral antibiotics
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Flucloxacillin (first-line for S. aureus)
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Amoxicillin-clavulanate if mixed infection suspected
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Consider MRSA coverage if resistant or high-risk population
Complications
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Cellulitis – deeper infection of dermis and subcutaneous tissue
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Post-streptococcal glomerulonephritis – mainly after streptococcal impetigo
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Scarring or pigment changes
PLAB-Style Questions
Q1: A 4-year-old presents with multiple honey-colored crusted lesions around the nose and mouth. Mild itching is present. Most likely diagnosis?
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A. Folliculitis
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B. Impetigo
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C. Eczema
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D. Herpes simplex
✅ Answer: B. Impetigo
Q2: A patient has extensive non-bullous impetigo on the arms and legs. Best initial management?
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A. Topical mupirocin only
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B. Oral flucloxacillin
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C. Oral acyclovir
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D. Topical corticosteroids
✅ Answer: B. Oral flucloxacillin
(Extensive disease requires systemic antibiotics.)
High-Yield Pearls
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Impetigo = superficial vesicles/pustules with honey-colored crusts, usually on face/extremities.
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Most common in young children; highly contagious.
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Topical antibiotics for mild, localized disease; systemic antibiotics for extensive involvement.
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Complications: cellulitis, post-streptococcal glomerulonephritis.
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Distinguish from folliculitis (lesions centered on hair follicles) and herpes simplex (grouped vesicles, painful).
