Background
Ecthyma gangrenosum (EG) is a well-recognized but uncommon cutaneous infection classically associated with Pseudomonas aeruginosa. [1] It was first described in association with Pseudomonas septicemia by Barker in 1897 and was later given the name ecthyma gangrenosum by Hitschmann and Kreibich.
EG usually occurs in patients who are critically ill and immunocompromised. Although it is almost always a sign of pseudomonal sepsis, there have been instances in which other bacteria (eg, including Proteus species, Escherichia coli, and methicillin-resistant Staphylococcus epidermidis, have been implicated in similar lesions. [2, 3, 4] Fungi have been implicated as well in some cases. [5] Not all cases have been associated with sepsis. [6, 7, 8, 9]
The characteristic lesions of EG are hemorrhagic vesicles or pustules that evolve into necrotic ulcers with a tender erythematous border (see the image below).
Violaceous plaques and necrotic ulcers on the abdomen of a renal transplant patient. Tissue cultures were positive for Pseudomonas aeruginosa.
EG requires prompt diagnosis and treatment with antibiotics that are appropriately selected for the underlying etiology. If the lesion fails to respond to antimicrobials, surgical debridement of the spreading necrotic lesion may be required. (See Treatment.)
Pathophysiology
Impaired humoral or cellular immunity leads to increased susceptibility to infections with P aeruginosa or other pathogens. In addition, breakdown of mechanical defensive barriers, such as the skin and mucosa, may allow infectious organisms to disseminate.
The lesions of EG result from perivascular bacterial invasion of arteries and veins in the dermis and subcutaneous tissues, which produces a necrotizing vasculitis. [10] Perivascular involvement can occur via hematogenous seeding of the skin in bacteremic patients or via direct inoculation through the skin in nonbacteremic patients. Extravasation of blood, edema, and necrosis around the vessel interrupt the blood supply to these tissues, resulting in secondary ischemic necrosis of the epidermis and dermis, which manifests as nodular lesions that rapidly evolve through stages of central hemorrhage, ulceration, and necrosis.
Etiology
EG is typically and most commonly caused by P aeruginosa; however, EG-like lesions have been observed in patients with other bacterial and fungal infections. [11]
Gram-positive bacteria that cause ecthyma and EG-like lesions include the following:
-
Staphylococcus aureus [12]
-
Streptococcus pyogenes
Gram-negative bacteria that cause ecthyma and EG-like lesions include the following:
-
Aeromonas hydrophila
-
Burkholderia cepacia [13]
-
Chromobacterium violaceum [14]
-
Citrobacter freundii
-
Corynebacterium diphtheriae
-
E coli
-
Klebsiella pneumoniae
-
Morganella morganii [15]
-
Neisseria gonorrhoeae
-
P aeruginosa
-
Pseudomonas stutzeri
-
Serratia marcescens
-
Vibrio vulnificus
-
Yersinia pestis
-
Xanthomonas maltophilia
Fungi that cause ecthyma and EG-like lesions include the following:
-
Aspergillus fumigatus
-
Candida albicans [16]
-
Curvularia species [17]
-
Exserohilum species
-
Fusarium solani [18]
-
Mucor and Rhizopus species
-
Pseudallescheria boydii [17]
-
Neoscytalidium dimidiatum
Viral causes include herpes simplex virus (HSV). [19]
Epidemiology
EG develops in 1.3-13% of patients with P aeruginosa sepsis and in a smaller percentage of patients who are not bacteremic.
EG may affect patients of any age, though it is more commonly reported in infants and elderly patients, whose immune systems may be underdeveloped or compromised (eg, by chronic granulomatous disease [20] ).
No sexual predilection is evident in the overall prevalence of EG; however, a slight predominance of bacteremic EG in males (male-to-female ratio, 1.3-5:1) and nonbacteremic EG in females (female-to-male ratio, 2.3:1) has been observed.
Prognosis
Delays in diagnosis and treatment have been associated with a high mortality. Rates of death from Pseudomonas sepsis in immunocompromised persons have ranged from 18% to 96%, whereas the mortality of EG in nonbacteremic patients has been reported to be 15.4%. In a study (N = 82) from a single integrated health system, the overall mortality was approximately 34%. [21] Mortality was higher in patients with sepsis or immunocompromise than in those without.
Factors associated with a poor prognosis include the following:
-
Multiple lesions
-
Delayed diagnosis and institution of appropriate antibiotics
-
Persistent neutropenia
-
High bacteremic load
-
Repeated catheterization and instrumentation
Coexisting conditions in patients prone to Pseudomonas sepsis may contribute to morbidity and mortality.
-
Violaceous plaques and necrotic ulcers on the abdomen of a renal transplant patient. Tissue cultures were positive for Pseudomonas aeruginosa.
