Characteristics of Impetigo Lesions
Impetigo presents in two main forms: nonbullous impetigo (70% of cases) and bullous impetigo (30% of cases), each with distinct clinical characteristics caused by Staphylococcus aureus and/or Streptococcus pyogenes. 1
Nonbullous Impetigo
- Begins as erythematous papules that rapidly evolve into vesicles and pustules 2
- Characterized by honey-colored crusts on the face and extremities 1
- Caused by Staphylococcus aureus, Streptococcus pyogenes, or both in combination 2
- Lesions typically rupture, creating crusted, erythematous erosions 3
- Most commonly affects exposed areas such as the face and extremities 1
Bullous Impetigo
- Caused exclusively by toxin-producing strains of S. aureus 2
- Characterized by fragile, thin-roofed vesicopustules that form when toxins cleave the dermal-epidermal junction 3, 2
- Lesions may rupture, creating crusted, erythematous erosions, often surrounded by a collar of the roof's remnants 3
- More likely to affect intertriginous areas 1
- Presents with large, flaccid bullae containing clear fluid that later becomes cloudy 1, 4
Ecthyma (Deeper Form of Impetigo)
- Deeper infection than regular impetigo, extending into the dermis 2
- Begins as vesicles that rupture, resulting in circular, erythematous ulcers with adherent crusts 2
- Caused by S. aureus and/or streptococci 2
- More likely to cause scarring than regular impetigo 1
Clinical Course and Distribution
- Most commonly affects children, particularly those between 2-5 years of age 1, 5
- Highly contagious and can spread rapidly through close contact 6, 5
- Usually resolves within 2-3 weeks without scarring if properly treated 1
- Can occur as a primary infection or secondarily infect pre-existing skin conditions (eczema, insect bites, herpetic lesions) 1
- Most frequently affects exposed areas such as the face and extremities 1
Diagnostic Features
- Diagnosis is primarily clinical based on characteristic appearance 6
- Gram stain and culture of pus or exudates from skin lesions can help identify the causative organism 3
- Cultures are particularly important in cases of treatment failure, suspected MRSA, or recurrent infections 2
Complications
- Complications are rare, with poststreptococcal glomerulonephritis being the most serious 1
- Systemic antimicrobials should be used during outbreaks of poststreptococcal glomerulonephritis to eliminate nephritogenic strains of S. pyogenes 3, 2
Understanding these characteristic lesions is essential for prompt diagnosis and appropriate treatment, which helps prevent spread and potential complications of impetigo.