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BACKGROUND AND CLINICAL INFORMATION: Head

Pathogen: Hartmannella-Acanthamoeba group, Balamuthia. Acanthoamoeba specis have an special trophism of for the brain.

Acanthoamoeba:

Route of entry: The presence of Acanthoamoeba species is ubiquitous and they may be part of the normal flora, route of entrance is unclear.
Anatomic sites:
Any where of the brain can be involved but the cerebellum, brain stem, thalamus and anterior parts of the cerebrum are most severely affected.
The spinal cord is spared.
Can present as space occupying lesion.

Clinical features:

Can be found in age from 5 to 60 years. No history of swimming or exposure to contaminated water.
Present as a subacute or chronic meningoencephalitis. Symptoms include headache, fever, mental abnormalities, hemiparesis and seizures.
Patients may be immunocomprised or have HIV infection, or having some chronic disease such as diabetes.

GROSS:

Features of diffuse meningitis with brain edema, focal softening, hemorrhage and necrosis.

HISTOPATHOLOGY AND IMMUNOHISTOCHEMISTRY: Head

Subacute or chronic meningitis. Also encephalitis characterized by vasculitis, thrombi formation and organization, and giant cell formation (except in immunosuppressed host). Thrombosed vessels may be seen. Microglial proliferation and reactive gliosis.

Trophozoites are 15-45 mm in diameter and have a clear nucleus with a dense central nucleolus; they cytoplasm contains granules and vacuoles. They may be found in the vessel wall and in areas free of inflammatory cell infiltration.

Cystic forms found in the tissue are 15-20 mm in diameter and are characterized by a wrinkled double wall around a stellate endocyst.

Viable organism: In contrast to Naegleria, they move slowly.

REFERENCE:

Seijo Martinez M, Gonzalez-Mediero G, Santiago P, Rodriguez De Lope A, Diz J, Conde C, Visvesvara GS. Granulomatous amebic encephalitis in a patient with AIDS: isolation of acanthamoeba sp. Group II from brain tissue and successful treatment with sulfadiazine and fluconazole. J Clin Microbiol. 2000 Oct;38(10):3892-5.

Pirehma M, Suresh K, Sivanandam S, Anuar AK, Ramakrishnan K, Kumar GS. Field's stain--a rapid staining method for Acanthamoeba spp. Parasitol Res. 1999 Oct;85(10):791-3.

Koide J, Okusawa E, Ito T, Mori S, Takeuchi T, Itoyama S, Abe T. Granulomatous amoebic encephalitis caused by Acanthamoeba in a patient with systemic lupus erythematosus. Clin Rheumatol. 1998;17(4):329-32.

Sell JJ, Rupp FW, Orrison WW Jr. Granulomatous amebic encephalitis caused by acanthamoeba. Neuroradiology. 1997 Jun;39(6):434-6.

Di Gregorio C, Rivasi F, Mongiardo N, De Rienzo B, Wallace S, Visvesvara GS. Acanthamoeba meningoencephalitis in a patient with acquired immunodeficiency syndrome. Arch Pathol Lab Med. 1992 Dec;116(12):1363-5.

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Background Gross Histopathology & Immunohistochemistry Reference