Description, Causes and Risk Factors:
Ecthyma gangrenosum is a characteristic necrotic and bullous skin lesion, manifestation of severe and invasive infection caused most commonly by Pseudomonas aeruginosa [a bacterial species found in soil, water, and commonly in clinical specimens (wound infections, infected burn lesions, urinary tract infections); the causative agent of blue pus; occasionally pathogenic for plants; usually causes infections in humans in whom there is a defect in host defense mechanisms. It is the type species of the genus Pseudomonas]. However, in some cases, it may be caused by Klebsiella pneumoniae and other species of Pseudomonas like P. maltophilia, P. burkholderia, P. cepacia, etc. Most cases of ecthyma gangrenosum have been associated with concomitant septicemia but it may also rarely develop without bacteremia due to P. aeruginosa. Ecthyma gangrenosum is a well described entity which may occur with a frequency of 30% during the course of P. aeruginosa septicemia.
The characteristic clinical appearance is red macules that progress to central areas of necrosis surrounded by an erythematous halo. This lesion represents a formidable skin sign of a potentially life-threatening systemic infection. The main site of ecthyma gangrenosum lesions is the gluteal or perineal region (57%), although this lesion can spread to other body sites, in which metastatic lesions appear on both trunks and lower extremities. Another major clinical feature in almost all patients is the presence of neutropenia. This disease is a life-threatening septicemic infection and has a high mortality.
The exact mechanism of the pathogenesis of ecthyma gangrenosum caused by P. aeruginosa in neutropenic patients is poorly defined. The primary inciting factor appears to be the presence of numerous viable organisms at the point of involvement. Dissolution of the elastic lamina of blood vessels by Pseudomonas elastase allows for liberation of the bacilli into the subcutaneous tissues. Further prolific multiplication of the organism in subjacent tissue with elaboration of exotoxin A and proteases leads to the ulcerative lesion which is characterized by hemorrhage, encircled by a rim of reactive erythema. This cutaneous manifestation associated with P. aeruginosa exotoxin A production has also been reported by young.
Ecthyma gangrenosum is usually seen in immunocompromized patients with leukemia, lymphoma, other malignant diseases, severe burns or organ transplant, or in people receiving immunosuppressive therapy. However, it has been reported also in patients without previously identified medical problems. Most of them had a concurrent viral infection or had received recent antibiotic therapy. Ecthyma gangrenosum might be the first manifestation of an underlying medical problem and previously healthy patients should be followed closely in the future.
In neutropenic patients the clinicians should be aware of such skin manifestations and consider ecthyma gangrenosum as a likely diagnosis to avoid the life-threatening septicemic infection and mortality.
The lesion begins as a painless red macule that enlarges and becomes a slightly elevated papule. It evolves to a hemorrhagic bulla that ruptures, forming a gangrenous ulcer with a gray-black eschar surrounded by an erythematous halo. Classically, the pathogen is isolated from the skin lesions as well as from the blood. These lesions may occur anywhere, but are most usual on the anogenital region, buttocks, extremities, abdomen, axillae and rarely on the face.
A Gram stain of fluid from the central hemorrhagicpustule or bulla can facilitate rapid diagnosis. Theorganism can proliferate in blood, urine and tissuecultures. Histopathologically, ecthyma gangrenosumis characterized byepidermal necrosis with hemorrhage and dermalinfarction, usually accompanied by a mixed inflammatory cell infiltrate of lymphocytes, histiocytes andneutrophils. In general, acute mixed inflammatorycell infiltration and vascular proliferation are seen inthe dermis, often involving the subcutaneous tissue.Elastases produced by Pseudomonas destroy theelastic small vessels, leading to hemorrhage and release of organisms into the surrounding tissue. Protease and endotoxin A, elaborated by bacilli, areresponsible for direct tissue destruction and ulcerative lesions. Gram staining reveal Gram-negative bacilli and Pseudomonas aeruginosaproliferation in both blood and ulcer cultures.
Early diagnosis and aggressive therapy are important in the management of ecthyma gangrenosum. An antipseudomonal beta-lactam antibiotic with or without an aminoglycoside is appropriate for treatment of both bacteremic and non-bacteremic ecthyma gangrenosum. The absence of bacteremia is associated with the best outcome. Patients with Pseudomonas bacteremia have been reported to have a mortality rate of 38%. On the other hand, only two patients (15%) died in a review of 13 patients with ecthyma gangrenosum without bacteremia. In another study, the mortality rate was 7.5 % in the group of patients with skin lesions considered to be primary and 20% in the group of patients with skin lesions considered to be secondary to bacteremia.
To decrease the mortality of this disease, the treatment should include prompt recognition of the skin lesion, appropriate antibiotic coverage against Pseudomonas aeruginosa and surgical debridement.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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