Masked Intruder: Unraveling a Case of Granulomatous Amebic Encephalitis Mimicry
Jackie Martin1, Alice Sardarian2, Sydnie Jones1, Alexis Nelson1, Jessie Jacobson1
1Neurology, Brooke Army Medical Center, 2Uniformed Services University of the Health Sciences
Objective:
To report a rare case of granulomatous amebic encephalitis caused by Balamuthia mandrillaris in an immunocompetent patient.
Background:
Granulomatous amebic encephalitis (GAE) is an exceedingly rare disease with a mortality rate of over 90%. It can be caused by species such as Balamuthia mandrillaris, Acanthamoeba, or Sappinia pedata. Unlike primary amebic meningoencephalitis (PAM), which typically presents with an acute progression resulting in multiple lesions, GAE often follows a subacute to chronic course and is typically associated with a single space occupying lesion. Environmental exposures, including water, soil, and dust, are potential risk factors for amebic inoculation. Our case illustrates a novel presentation of amebic encephalitis that was misdiagnosed as herpes simplex virus (HSV) encephalitis.
Results:
An immunocompetent 78-year-old Hispanic male with a history of atrial fibrillation without recent travel or obvious environmental exposure presented with a two-week history of cough, acute-onset mixed aphasia, gait abnormalities, fatigue, and confusion. MRI revealed a large left anterior temporal lobe edematous hyperintensity mass with microhemorrhage, closely resembling HSV. Patient was empirically treated for presumed HSV encephalitis, based on imaging and inflammatory cerebrospinal fluid pattern despite negative HSV PCR. However, patient’s clinical status further deteriorated, and he had worsening vasogenic edema leading to threatened uncal herniation and necessitating a left hemicraniectomy. Regrettably, the patient died within three weeks of symptom onset, and the diagnosis of GAE due to Balamuthia mandrillaris was made postmortem by analysis of necrotic brain tissue. The only possible exposure identified was via soil during a recent yard renovation.
Conclusions:
GAE is often a fatal diagnosis due to its rapid progression and the challenges of early diagnosis. We hope this case underscores the importance of considering amebic encephalitis as a differential diagnosis, particularly when a patient does not respond to conventional broad-spectrum meningitis/encephalitis therapy.
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