Signs and Symptoms of Impetigo
Impetigo presents with two distinct clinical patterns: nonbullous impetigo (70% of cases) begins as erythematous papules that rapidly evolve into vesicles and pustules, which rupture to form characteristic honey-colored crusts on an erythematous base, while bullous impetigo (30% of cases) manifests as fragile, thin-roofed vesicopustules that rupture to create crusted, erythematous erosions often surrounded by a collar of remnant blister roof. 1
Nonbullous Impetigo (70% of cases)
The clinical progression follows a predictable pattern:
- Initial presentation: Erythematous papules appear first
- Rapid evolution: Within 4-6 days, these papules progress to vesicles and pustules 2
- Characteristic crusting: After rupture, the dried discharge forms the pathognomonic honey-colored crusts on an erythematous base 1, 3
- Location: Most commonly affects the face and extremities 3
- Causative organisms: Staphylococcus aureus and/or β-hemolytic streptococci (Streptococcus pyogenes) 1, 4
Bullous Impetigo (30% of cases)
This toxin-mediated variant has distinct features:
- Mechanism: Caused exclusively by S. aureus strains producing exfoliative toxin that cleaves the dermal-epidermal junction 1, 5
- Lesion appearance: Fragile, thin-roofed vesicopustules and large, flaccid bullae that rupture easily 1, 3
- After rupture: Creates crusted, erythematous erosions with a characteristic collar of remnant blister roof surrounding the lesion 1
- Preferred location: More likely to affect intertriginous areas (skin folds) 3
- Associated symptoms: Pruritus (itching) is common 5
Key Distinguishing Features
Important clinical pearl: Unlike staphylococcal scalded skin syndrome, bullous impetigo remains localized because the exfoliative toxins act within the skin rather than disseminating systemically 5. This is a critical distinction when evaluating a child with blistering skin lesions.
Common Clinical Context
- Age group: Most commonly affects children 2 to 5 years of age 2, 3, 4
- Primary vs. secondary: Can occur as primary skin infection or secondarily infect insect bites, eczema, or herpetic lesions 3
- Natural course: Both types typically resolve within 2-3 weeks without scarring if untreated 3
- Contagiousness: Highly contagious, with potential for household clusters 5
Ecthyma: A Deeper Variant
While not classic impetigo, ecthyma represents a related, deeper infection worth recognizing:
- Depth: Extends deeper than impetigo into the dermis 1
- Appearance: Vesicles rupture to form circular, erythematous ulcers with adherent crusts and surrounding erythematous edema 1
- Key difference: Unlike impetigo, ecthyma heals with scarring 1
- Causative organisms: S. aureus and/or streptococci 1
Clinical Diagnosis
The diagnosis is primarily clinical, based on the characteristic appearance of honey-colored crusts (nonbullous) or flaccid bullae with collarette remnants (bullous) 1, 2, 3. While Gram stain and culture of vesicle fluid, pus, or erosions can establish the causative organism, treatment without these studies is reasonable in typical cases 1.