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- A contagious, superficial, intraepidermal infection occurring prominently on exposed areas of the face and extremities, most often seen in children
- Primary impetigo (pyoderma): invasion of previously normal skin
- Secondary impetigo (impetiginization): invasion at sites of minor trauma (abrasions, insect bites, underlying eczema)
- Infected patients usually have multiple lesions.
- Cultures are positive in >80% cases for Staphylococcus aureus either alone or combined with group A β-hemolytic streptococci; S. aureus is the more common pathogen since the 1990s.
- Nonbullous impetigo: most common form of impetigo. Formation of vesiculopustules that rupture, leading to crusting with a characteristic golden appearance; local lymphadenopathy may occur.
- Bullous impetigo: staphylococcal impetigo that progresses from small to large flaccid bullae (newborns/young children) caused by epidermolytic toxin release; ruptured bullae leaving brown crust; less lymphadenopathy; trunk more often affected; <30% of patients
- Folliculitis: considered by some to be S. aureus impetigo of hair follicles
- Ecthyma: a deeper, ulcerated impetigo infection often with lymphadenitis
- System(s) affected: skin/exocrine
- Synonym(s): pyoderma; impetigo contagiosa; impetigo vulgaris
- Predominant sex: male = female
- Predominant age: children ages 2 to 5 years
In the United States: not reported but common
- Poststreptococcal glomerulonephritis may follow impetigo (in young children).
- Impetigo neonatorum may occur due to nursery contamination.
Etiology and Pathophysiology
- Coagulase-positive staphylococci: pure culture ~50–90%; more contagious via contact
- β-Hemolytic streptococci: pure culture only ~10% of the time (primarily group A)
- Mixed infections of streptococci and staphylococci are common; data suggest increasing importance of staphylococci over the past decades.
- Methicillin-resistant S. aureus (MRSA) detected in some cases
- Direct contact or insect vector
- Can result from contamination at trauma site
- Regional lymphadenopathy
- Warm, humid environment
- Tropical or subtropical climate
- Summer or fall season
- Minor trauma, insect bites, breaches in skin
- Poor hygiene, poverty, crowding, epidemics, wartime
- Familial spread
- Poor health with anemia and malnutrition
- Complication of pediculosis, scabies, chickenpox, eczema/atopic dermatitis
- Contact dermatitis (Rhus spp.)
- Contact sports
- Children in daycare
- Carriage of group A Streptococcus and Staphylococcus aureus
- Close attention to family hygiene, particularly hand washing among children
- Covering of wounds
- Avoidance of crowding and sharing of personal items
- Treatment of atopic dermatitis
Commonly Associated Conditions
- Malnutrition and anemia
- Crowded living conditions
- Poor hygiene
- Neglected minor trauma
- Any chronic/underlying dermatitis
- Can occur as coinfection with scabies
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