Background

Amoeba infection has become increasingly common with the appearance of AIDS and immunosuppressant agents. The most important amoebas include Acanthamoeba, Naegleria, and Balamuthia, and Entamoeba histolytica. The free-living amoebas, belonging to three groups: amoeboflagellates (Naegleria), Acanthamoebidae, and Leptomyxida (Balamuthia), are ubiquitous and have been isolated from air, soil, and water samples throughout the world.

OUTLINE

Epidemiology
Disease Associations
Pathogenesis
Laboratory/Radiologic/Other Diagnostic Testing
Gross Appearance and Clinical Variants
Histopathological Features and Variants
Special Stains/ Immunohistochemistry/ Electron Microscopy
Differential Diagnosis
Prognosis
Treatment
Commonly Used Terms
Internet Links

 

DISEASE ASSOCIATIONS	CHARACTERIZATION
AIDS
Disseminated Acanthamoeba sinusitis in a patient with AIDS: a possible role for early antiretroviral therapy. Carter WW, Gompf SG, Toney JF, Greene JN, Cutolo EP. University of South Florida, Tampa, Florida, USA.	AIDS Read. 2004 Jan;14(1):41-9. Abstract quote   Acanthamoeba, a free-living ameba, has been reported to infect humans with subacute encephalitis, sinusitis, or keratitis. Multiple cases of Acanthamoeba sinusitis with dissemination have been reported in association with AIDS, with high mortality. We report successful treatment of a 35-year-old woman who presented with sinusitis that progressed to disseminated acanthamebiasis as her initial manifestation of AIDS. To our knowledge, our patient was one of the few and longest-lived survivors of disseminated Acanthamoeba infection with AIDS. As with other opportunistic infections, early aggressive therapy including HAART may alter the outcome in this almost uniformly fatal disease.

 

PATHOGENESIS

CHARACTERIZATION

Acanthamoebae

Acanthamoebae are free-living amoebas, existing in two forms: Trophozoite and the cyst Trophozoites are large (15 to 35 mm),6 single nucleus and prominent nucleolus, surrounded by a nuclear halo. The cytoplasm is abundant and granular Positive with Gomorìs methenamine-silver (GMS) stain The double-walled cysts, measuring 15̉20 mm,6 stain with periodic acid-Schiff (PAS) and (GMS)-The ectocyst is characteristically wavy and wrinkled. The inner endocyst is scalloped. The nucleus is eccentrically placed with a prominent nucleolus (karyosome), surrounded by a halo.

 

HISTOLOGICAL TYPES	CHARACTERIZATION
SKIN
Disseminated cutaneous acanthamebiasis: a case report and review of the literature. Paltiel M, Powell E, Lynch J, Baranowski B, Martins C. Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.	Cutis. 2004 Apr;73(4):241-8. Abstract quote The genus Acanthamoeba includes species of free-living soil and water ameba that have been implicated in a small number of human diseases. Acanthamoeba species have been identified as the etiologic agents in 2 well-defined clinical entities, amebic keratitis and granulomatous amebic encephalitis (GAE). Less commonly, Acanthamoeba species have been identified as the cause of disseminated disease in debilitated and immunocompromised patients. Cutaneous acanthamebiasis, often a reflection of disseminated disease, is an increasingly recognized infection since the emergence of acquired immunodeficiency syndrome (AIDS) and the use of immunosuppressive drugs. The disease portends a poor prognosis and is uniformly fatal if the infection involves the central nervous system (CNS). We describe a patient with advanced AIDS who presented with disseminated cutaneous lesions, headache, and photophobia, and in whom a diagnosis of cutaneous acanthamebiasis was made based on the results of a skin biopsy. A multidrug therapeutic regimen was begun that included sulfadiazine; the patient responded favorably to treatment. This paper also reviews 36 previously reported cases of cutaneous acanthamebiasis with delineation of clinical, diagnostic, histologic, and prognostic features, as well as discusses treatment options.
Disseminated acanthamoebiasis presenting as lobular panniculitis with necrotizing vasculitis in a patient with AIDS Arlene Sylvia Rosenberg1 and Michael B. Morgan	Journal of Cutaneous Pathology 2001;28 (6): 307-313 Abstract quote Background: Disseminated acanthamoebiasis is a rare entity, almost exclusively occurring in the immunocompromised host. Methods: We report an unusual case of a 35-year-old female with recurrent sinusitis and multiple skin nodules demonstrating a necrotizing panniculitis, shown to be due to disseminated acanthamoebiasis. Results: Histologic sections showed a neutrophilic lobular panniculitis with 20- to 30-mm trophozoites consistent with Acanthamoeba species. Conclusions: A review the literature shows that the histopathological presentation of acanthamoebiasis often eludes initial diagnostic attempts and that central nervous system (CNS) involvement is frequent and ultimately fatal. When amoebiasis is suspected, knowledge of the trophozoite and cyst forms may be helpful in distinguishing Acanthamoeba species from Entamoeba histolytica.
Disseminated acanthamebiasis in patients with AIDS. A report of five cases and a review of the literature. Murakawa GJ, McCalmont T, Altman J, Telang GH, Hoffman MD, Kantor GR, Berger TG. Department of Dermatology, University of California at San Francisco, USA.	Arch Dermatol. 1995 Nov;131(11):1291-6. Abstract quote   BACKGROUND: Acanthamoeba and Leptomyxida are free-living amebae that cause granulomatous amebic encephalitis, a rare, slowly progressive, fatal neurologic process seen in immunosuppressed hosts. In addition, these organisms produce disseminated cutaneous lesions and involve other organs, particularly in patients with the acquired immunodeficiency syndrome (AIDS). RESULTS: We report five cases of disseminated acanthamebiasis in patients with AIDS, each with cutaneous manifestations but lacking central nervous system involvement. The medial CD4+ T-cell count was 0.024 x 10(9)/L. Skin lesions included pustules, subcutaneous and deep dermal nodules, and ulcers, most often seen on the extremities and face. Histopathologically, both pustular and vasculitic changes were observed; in all cases, the microscopic identification of organisms was difficult because of the macrophagelike appearance of the microbes in routine sections. CONCLUSIONS: Skin lesions are the most common reported presentation of infections caused by Acanthamoeba and Leptomyxida organisms in patients with AIDS, a minority of whom have central nervous system manifestations. A high index of suspicion is necessary for both the dermatologist and the dermatopathologist. Prognosis is guarded, but early treatment using a combination of intravenous pentamidine and oral fluconazole, sulfadiazine, and flucytosine may be beneficial.

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Last Updated June 8, 2005

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