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Impetigo

Updated: Jun 29, 2022

Presentation

Impetigo is characterized by erythematous lesions that are covered with a honey-coloured crust. The lesions are usually asymptomatic, but they can be pruritic. The lesions begin as macules and papules, but then quickly fill with fluid and rupture. The lesions are highly contagious and can be transmitted to other areas of the body (i.e., autoinoculation) and to other persons. There is often a history of close contact with similar lesions.

Non-bullous impetigo

There are small vesicles that quickly burst and often are not present upon evaluation.

Bullous impetigo

There are large flaccid bullae. In both of these subtypes, the fluid filled lesions rupture and result in a superficial erosion.

Ecthyma

The lesions extend into the dermis resulting in ulceration with violaceous borders.



Evaluation

A clinical diagnosis is usually made based on the characteristic skin findings. Although a gram stain and culture of the fluid within the lesion is generally recommended, treatment in typical cases can commence without these investigations. Common indications for cultures are listed in the table below.

Indications for bacterial culture and sensitivity of pus

​Local outbreak

Suspicion of MRSA

Treatment failure

​Development of poststreptoccal glomerulonephritis

Indications for nasal culture

Recalcitrant impetigo

Management

Topical antibiotics (e.g., mupirocin, retapamulin, fuscidic cid) are recommended for infections with a limited number of lesions. Although the condition is self-limited, treatment is recommended to prevent the progression of the illness and to prevent the spread of infection to other people. Children are allowed to return to school following 24 hours of antibiotic therapy.

Indications for systemic antibiotics (e.g., cephalexin)

​Ecthyma

Widespread infection

​Systemic involvement

Local outbreak of poststreptococcal glomerulonephritis

Complications

Poststreptococcal glomerulonephritis is a potential complication of impetigo. It occurs when the pathogenic organism is a nephritogenic strain of group A beta-hemolytic streptococci.


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References

  1. Dajani AS, Ferrieri P, Wannamaker LW. Natural history of impetigo. II. Etiologic agents and bacterial interactions. J Clin Invest. 1972 Nov;51(11):2863-71. doi: 10.1172/JCI107109. PMID: 4263498; PMCID: PMC292435.

  2. Cole C, Gazewood J. Diagnosis and treatment of impetigo. Am Fam Physician. 2007 Mar 15. 75(6):859-64.

  3. Darmstadt GL, Lane AT. Impetigo: an overview. Pediatr Dermatol. 1994 Dec;11(4):293-303. doi: 10.1111/j.1525-1470.1994.tb00092.x. PMID: 7899177.

  4. Moran GJ, Amii RN, Abrahamian FM, Talan DA. Methicillin-resistant Staphylococcus aureus in community-acquired skin infections. Emerg Infect Dis. 2005 Jun. 11(6):928-30.

  5. Stevens DL, Bisno AL, Chambers HF, Dellinger EP, Goldstein EJ, Gorbach SL, Hirschmann JV, Kaplan SL, Montoya JG, Wade JC. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the infectious diseases society of America. Clin Infect Dis. 2014 Jul 15;59(2):147-59. doi: 10.1093/cid/ciu296. Epub 2014 Jun 18. PMID: 24947530.

  6. Koning S, van der Sande R, Verhagen AP, van Suijlekom-Smit LW, Morris AD, Butler CC, Berger M, van der Wouden JC. Interventions for impetigo. Cochrane Database Syst Rev. 2012 Jan 18;1(1):CD003261. doi: 10.1002/14651858.CD003261.pub3. PMID: 22258953; PMCID: PMC7025440.



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