What is Impetigo?
Impetigo is a highly contagious superficial bacterial skin infection of the epidermis, predominantly affecting children aged 2-5 years, characterized by honey-colored crusted lesions or fluid-filled blisters caused by Staphylococcus aureus and/or Streptococcus pyogenes. 1, 2
Clinical Presentation and Types
Impetigo presents in two principal forms:
Nonbullous Impetigo (70% of cases)
- Caused by S. aureus and/or S. pyogenes 2
- Characterized by discrete purulent lesions with distinctive honey-colored crusts 3, 1
- Most commonly affects the face and extremities 1, 2
- May occur as primary infection or secondarily infect insect bites, eczema, or herpetic lesions 2
Bullous Impetigo (30% of cases)
- Caused exclusively by S. aureus 2
- Results in large, flaccid fluid-filled blisters that rupture, leaving thin brown crusts 1, 2
- More likely to affect intertriginous areas (skin folds) 2
Epidemiology and Transmission
- Most common bacterial skin infection in children worldwide, with a global disease burden exceeding 140 million cases 4
- Incidence decreases with age 4
- Spreads readily through direct skin-to-skin contact or sharing of towels, clothing, and bedding 1
- Bacteria colonize the skin surface and enter through minor cuts, insect bites, or scratches 1
Causative Organisms
The primary pathogens are Gram-positive bacteria:
- Staphylococcus aureus is the predominant pathogen 3, 2
- Streptococcus pyogenes (Group A Streptococcus) 3, 2
- Rising concern for community-acquired MRSA (CA-MRSA) as an etiological agent 3, 1
Natural History and Complications
- Both types typically resolve spontaneously within 2-3 weeks without scarring if untreated 2, 5
- Complications are rare 2
- The most serious complication is post-streptococcal glomerulonephritis 2
- Treatment is recommended despite self-limited nature to relieve discomfort, improve cosmetic appearance, prevent spread, and reduce risk of complications 5
Diagnostic Approach
- Diagnosis is primarily clinical, based on the characteristic appearance of honey-colored crusts or bullae 2, 5
- Culture of vesicle fluid, pus, or erosions should be obtained if treatment failure occurs, MRSA is suspected, or in cases of recurrent infections 6
- Physical examination reveals erythema, tenderness, and induration in the affected areas 3