Updated: 4/7/2017

Impetigo

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Snapshot
  • A 10-day-old girl is brought to the pediatrician by her mother after noticing multiple blisters. The mother states that some of the blisters have ruptured and left behind a ring of crust. On physical examination there is two 3 cm lesions on her axillae and several smaller bullae without any erythema in the groin. A superficial wound culture grows Staphylococcus aureus. She is subsequently started on topical antibiotics.
Introduction
  • Clinical definition
    • superficial contagious bacterial skin infection which can be divided into
      • nonbullous impetigo (most common) which is
        • caused by Staphylococcus aureus or group A streptococci
      • bullous impetigo
        • caused by Staphylococcus aureus toxin which is a
          • localized form of staphylococcal scalded skin syndrome
  • Epidemiology
    • incidence
      • 20.5 per 1000 person-years
      • most common bacterial skin infection in children
    • demographics
      • occurs commonly in children
    • most common pathogen
      • Staphylococcus aureus
      • group A streptococcus
    • most common location
      • on face and arms
    • risk factors
      • summer weather
      • disruption of skin leading to secondary infection of nonbullous impetigo
        • atopic dermatitis
  • Pathophysiology
    • superficial skin blister ruptures and forms a crust
  • Prognosis
    • survival with treatment
      • very good
Presentation
  • Nonbullous impetigo
    • physcal exam
      • single red macule or papule → vesicle surrounded by erythema → honey-crusted pustules
  • Bullous impetigo
    • physical exam
      • progression from vesicle → flaccid bullae without erythema → crusted erosion
        • ruptured bullae with yellow collarette from crusts
Studies
  • Labs
    • positive Gram stain
    • positive superficial wound culture
Differential
  • Herpes simplex virus
    • vesicles on erythematous base (bullous impetigo typically has no erythema)
  • Pemphigus foliaceus
    • erythema with scaling and crusting
Treatment
  • Medical
    • topical antibiotics
      • indications
        • local involvement of disease
    • oral antibiotics
      • indications
        • widespread involvement of disease
Complications
  • Spread to other members of the family
    • impetigo is highly contagious
    • cover open skin lesions
  • Acute post-streptococcal glomerulonephritis
    • 1-5% of patients with nonbullous impetigo
 

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