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Impetigo

Last updated: December 18, 2020

Summary

Impetigo is an infectious, predominantly pediatric skin disease caused by the bacteria Staphylococcus aureus or, less commonly, Streptococcus pyogenes. There are both bullous and nonbullous variants. The disease causes honey-colored, crusted lesions with surrounding erythema and typically affects the face, but may also manifest on the extremities. While the diagnosis is usually made based on clinical findings, it can be confirmed with a bacterial culture. The first-line treatment for mild impetigo is a topical antibiotic (mupirocin), which typically resolves the infection without complications. An additional systemic antibiotic may be indicated in more severe cases.

Epidemiology

  • Age
    • Primarily affects children (especially between 2–6 years of age) [1]
    • Impetigo is highly contagious and can cause epidemics in preschools or schools. [2]
  • Prevalence: high in resource-limited countries

Impetigo is the most common bacterial skin infection among children.

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Clinical features

Most common manifestations of impetigo [5]
Nonbullous impetigo Bullous impetigo
Epidemiology [6]
  • ∼ 70% of cases
  • ∼ 30% of cases
Lesions
  • Papules, which turn into small vesicles surrounded by erythema and/or pustules
    • Vesicles and pustules can rupture
    • Oozing secretion that dries forms honey-colored crusts that heal without scarring
  • May be pruritic (especially pustules) but is rarely painful [7]
  • Negative Nikolsky sign [8]
  • Vesicles that grow to form large, flaccid bullae, which go on to rupture and form thin, brown crusts
  • Positive Nikolsky sign (lateral traction causes sloughing of the skin) [9]
Distribution pattern
  • Face (most common), especially around the nose and mouth
  • Extremities
  • Trunk and upper extremities
Other findings
  • Systemic signs (e.g., fever, malaise, weakness) in severe cases
  • Rare manifestation: ecthyma
    • Ulcerative impetigo that extends into the dermis
    • Manifests as a coin-sized, superficial ulcer with a punched-out appearance

Impetigo should be suspected in children presenting with honey-colored crusts around the mouth and nose.

Diagnostics

  • Generally diagnosed based on clinical presentation
  • Microbiological culture [10]
    • Assists with detection of the causative pathogen
    • Indications: inconclusive diagnosis, recurrence despite treatment

Differential diagnoses

See “Differential diagnosis of scaling.” [5][11]

The differential diagnoses listed here are not exhaustive.

Treatment

Complications

We list the most important complications. The selection is not exhaustive.

Prevention

  • Advise patients and caregivers to wash hands regularly.
  • To prevent the spread of the disease, children should receive antibiotic treatment for at least 24 hours before returning to daycare or school.

References

  1. Sladden MJ. Common skin infections in children. BMJ. 2004; 329 (7457): p.95-99. doi: 10.1136/bmj.329.7457.95 . | Open in Read by QxMD
  2. Bowen AC, Mahé A, Hay RJ. The Global Epidemiology of Impetigo: A Systematic Review of the Population Prevalence of Impetigo and Pyoderma. PLoS One . 2015; 10 (8). doi: 10.1371/journal.pone.0136789 . | Open in Read by QxMD
  3. Bukowski M, Wladyka B, Dubin G. Exfoliative Toxins of Staphylococcus aureus. Toxins (Basel). 2010; 2 (5): p.1148-1165. doi: 10.3390/toxins2051148 . | Open in Read by QxMD
  4. Amagai M, Yamaguchi T, Hanakawa Y, Nishifuji K, Sugai M, Stanley JR. Staphylococcal exfoliative toxin B specifically cleaves desmoglein 1. J Invest Dermatol.. 2002; 118 (5): p.845-850. doi: 10.1046/j.1523-1747.2002.01751.x . | Open in Read by QxMD
  5. Baddour LM. Impetigo. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/impetigo.Last updated: September 11, 2016. Accessed: May 4, 2017.
  6. Bolognia J, Jorizzo J, Schaffer J. Dermatology: 2-Volume Set. Elsevier ; 2012
  7. HOLLY HARTMAN-ADAMS; CHRISTINE BANVARD; and GREGORY JUCKETT. Impetigo: Diagnosis and Treatment. American Family Physician. 2014 .
  8. Philip Watkins. Impetigo: aetiology, complications and treatment options. Nursing Standard. 2005 .
  9. Salopek TG. Nikolsky's sign: is it 'dry' or is it 'wet'?. Br J Dermatol. 1997; 136 (5): p.762-7.
  10. Rafik Bourayou, Nolwenn Le Sache, Isabelle Kone-Paut. Positive Nikolsky Sign due to Staphylococcal Scaled Skin Syndrome. The Journal of Pediatrics. 2011 .
  11. Cole C, Gazewood J. Diagnosis and Treatment of Impetigo. Am Fam Physician. 2007; 75 (6): p.859-864.
  12. Hartman-Adams H, Banvard C, Juckett G. Impetigo: Diagnosis and Treatment. Am Fam Physician. 2014; 90 (4): p.229-235.