Description

• A contagious, superficial, intraepidermal infection occurring prominently on exposed areas of the face and extremities
• 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 more common pathogen since 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 rapidly to small-to-large flaccid bullae (newborns/young children) caused by epidermolytic toxin release; 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; Fox impetigo

Epidemiology

• Predominant sex: Male = Female
• Predominant age: Children ages 2–5 years

• Poststreptococcal glomerulonephritis may follow impetigo (in young children).
• Impetigo neonatorum may occur due to nursery contamination.

Risk Factors

• Warm, humid environment
• Tropical or subtropical climate
• Summer or fall season
• Minor trauma, insect bites
• 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.)
• Burns
• Contact sports
• Children in daycare
• Possibly tobacco exposure
• Carriage of group A Streptococcus and S. aureus

General Prevention

• 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

Etiology

• Coagulase-positive staphylococci: Pure culture ~50–90%; more contagious via contact
• β-hemolytic streptococci: Pure culture only ~10% of the time
• Mixed infections of streptococci and staphylococci common; data suggest increasing importance of staphylococci over past 20 years (1)
• Direct contact or insect vector
• Can result from contamination at trauma site
• Regional lymphadenopathy

Commonly Associated Conditions

• Malnutrition and anemia
• Crowded living conditions
• Poor hygiene
• Neglected minor trauma
• Any chronic/underlying dermatitis