Ecthyma and impetigo

Updated September 13, 2023

Background

Overview

Definition

Impetigo is a highly contagious bacterial infection of the superficial layers of the epidermis. Ecthyma is a deeply ulcerated form of impetigo that extends into the dermis.

Pathophysiology

Impetigo is nearly always caused by S. aureus and/or β-hemolytic Streptococcus species. Community-acquired MRSA is an increasingly frequent etiological agent.

Epidemiology

Impetigo predominantly affects children. In patients under 18 years of age, the incidence of impetigo is estimated at 206 per 100,000 person-years.

Disease course

Impetigo begins as erythematous papules that rapidly evolve into vesicles and pustules that rupture, with the dried discharge forming honey-colored crusts on an erythematous base. Ecthyma begin as vesicles that rupture, resulting in circular, erythematous ulcers with adherent crusts, often with surrounding erythematous edema.

Prognosis and risk of recurrence

Acute poststreptococcal glomerulonephritis is a serious complication that affects between 1 and 5 percent of patients with nonbullous impetigo. Rheumatic fever does not appear to be a potential complication of impetigo. Impetigo usually resolves without scarring within two weeks if left untreated. Unlike impetigo, ecthyma heals with scarring.

Guidelines

Key sources

The following summarized guidelines for the evaluation and management of ecthyma and impetigo are prepared by our editorial team based on guidelines from the Surgical Infection Society Europe (SIS-E/WSES 2018), the Korean Society of Infectious Diseases (KSID/KDA/KOA/KSC 2017), the Infectious Diseases Society of America (IDSA 2014,2011), and the American Academy of Family Physicians (AAFP 2007).

Diagnostic investigations

Gram stain and culture: as per KDA/KOA/KSC/KSID 2017 guidelines, obtain Gram staining and bacterial culture testing on the pus or exudate from skin lesions, although consider initiating treatment without testing in typical cases.

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Medical management

Oral antibiotic therapy

As per SIS-E/WSES 2018 guidelines:

Administer an antibiotic active against Gram-positive bacteria in patients with impetigo.

Administer an antibiotic active against community-acquired MRSA in patients with impetigo at risk for MRSA and in patients not responding to first-line therapy.

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Specific circumstances

Pediatric patients: as per IDSA 2011 guidelines, consider applying topical mupirocin ointment (2%) in pediatric patients with impetigo and secondarily infected skin lesions (such as eczema, ulcers, or lacerations).

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