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Case Reports
. 2024 Jun 12;9(2):113-120.
doi: 10.3138/jammi-2023-0036. eCollection 2024 Jun.

Brainstorm: A Case of Granulomatous Encephalitis

Patrick Benoit  1   2 , Stephanie Wang  3 , Catherine Wang  4 , Arpita Chakravarti  1   2 , Julian A Villalba  5 , Ibne Karim M Ali  6 , Shantanu Roy  6 , Sarah Gh Sapp  7 , Sarah Reagan-Steiner  5 , Kristoff Nelson  4 , Romain Cayrol  8 , Me-Linh Luong  1   2 , Sophie Grand'Maison  3 , Michaël Desjardins  1   2
Affiliations
Case Reports

Brainstorm: A Case of Granulomatous Encephalitis

Patrick Benoit et al. J Assoc Med Microbiol Infect Dis Can. .

Abstract
in English, French

Background: Free-living amoebas (FLAs) can cause severe and fatal central nervous system infections that are difficult to diagnose.

Methods: We present the case of a 74-year-old immunocompetent woman admitted for focal neurological symptoms with enhancing lesions in the right cerebellar hemisphere. A first cerebral biopsy showed granulomatous inflammation, but no microorganisms were identified. After transient clinical improvement, she eventually deteriorated 4 months after initial presentation, with an MRI confirming multiple new masses affecting all cerebral lobes.

Results: A second brain biopsy revealed granulomatous and acute inflammation with organisms containing a large central nucleus with prominent karyosome, consistent with FLAs. Immunohistochemical and polymerase chain reaction assays performed at CDC were positive for Acanthamoeba spp, confirming the diagnosis of granulomatous amoebic encephalitis (GAE) caused by Acanthamoeba spp. The patient was treated with combination therapy recommended by CDC, but died a few days later. Upon histopathological rereview, amoebic cysts and trophozoites were identified by histochemical and immunohistochemical methods in the first cerebral biopsy.

Conclusion: FLA infections can be challenging to diagnose because of the low incidence, non-specific clinical and radiological presentation, lack of accessible diagnostic tools, and clinicians' unfamiliarity. This case highlights the importance of recognizing FLA as a potential cause of granulomatous encephalitis, even in the absence of risk factors, as early treatment might be associated with favourable outcomes in case reports. When suspected, CDC laboratories offer tests to confirm the diagnosis promptly.

Historique: Les amibes libres peuvent causer des infections du système nerveux central graves et fatales qui sont difficiles à diagnostiquer.

Méthodologie: Les auteurs présentent le cas d'une femme immunocompétente de 74 ans hospitalisée à cause de symptômes neurologiques focaux avec lésions rehaussantes dans l'hémisphère cérébelleux droit. Une première biopsie cérébrale a révélé une inflammation granulomateuse, mais aucun microorganisme n'a été décelé. Après une amélioration clinique transitoire, son état s'est détérioré quatre mois après la première consultation, et l'IRM a confirmé de multiples nouvelles masses touchant tous les lobes cérébraux.

Résultats: Une deuxième biopsie cérébrale a révélé une inflammation granulomateuse aiguë par des organismes dont les gros noyaux centraux et les caryosomes volumineux étaient évocateurs d'amibes libres. L'immunohistochimie et l'amplification en chaîne par polymérase effectuées aux CDC se sont avérés positives pour Acanthamoeba spp, ce qui a confirmé un diagnostic d'encéphalite amibienne granulomateuse causée par Acanthamoeba spp. La patiente a reçu une polythérapie recommandée par les CDC, mais est malheureusement décédée quelques jours plus tard. À la reprise de l'analyse histopathologique, des kystes amibiens et des trophozoïtes ont été décelés dans la première biopsie cérébrale par des méthodes histochimiques et immunohistochimiques.

Conclusion: Les infections par des amibes libres peuvent être difficiles à diagnostiquer en raison de leur faible incidence, de leur présentation clinique et radiologique non spécifique, de l'absence d'outils diagnostiques accessibles et de la méconnaissance des cliniciens. Ce cas renforce l'importance d'inclure les amibes libres dans les causes potentielles d'encéphalite granulomateuse, même en l'absence de facteurs de risque, car un traitement rapide a été associé à des résultats favorables dans certains rapports de cas. Lorsqu'on en soupçonne la présence, les laboratoires des CDC offrent des tests pour confirmer rapidement le diagnostic.

Keywords: Acanthamoeba; Balamuthia mandrillaris; free-living amoebas; granulomatous amoebic encephalitis.

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Conflict of interest statement

The findings and conclusions of this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention (CDC).

Figures

Figure 1:
Figure 1:. MRI imaging at initial presentation
(A) FLAIR and (B) T2 without contrast: hyperintensity of the right cerebellar hemisphere and the vermis (arrow) compatible with edema. (C) Diffusion and (F) ADC map: no evidence of restricted diffusion. (D) T1 without contrast and (E) T1 with contrast: clusters of cystic/necrotic enhancement with patchy enhancement (arrow) extending to the left cerebellum and signs of leptomeningeal involvement
Figure 2:
Figure 2:. Histopathological features of the second biopsy
(A) Hematoxylin and eosin-stained section of the frontal lobe lesion brain biopsy collected on the hospital 2nd day of the patient's second admission showed small, rounded cells with foamy, microvacuolated cytoplasm, and central nucleus with prominent karyosome, which were consistent with amoebas in their trophozoite stage (circled). Neutrophilic satellitosis surrounding trophozoites was prominently seen. (B) Immunohistochemistry (IHC) testing with a polyclonal antibody assay targeting Acanthamoeba healyi antigens and known to cross-react with other Acanthamoeba spp highlights abundant trophozoites with an extensive and strong granular pattern of staining in areas of inflammation. Microphotographs provided by Infectious Diseases Pathology Branch (IDPB) laboratory at the Centers for Disease Control and Prevention
Figure 3:
Figure 3:. Acanthamoeba spp culture on non-nutrient agar
Trophozoites leave tracks as they eat the bacteria on non-nutrient agar on the left. Trophozoites and double-walled cysts are visible under magnification on the right. Photos provided by Hôpital Maisonneuve-Rosemont
Figure 4:
Figure 4:. Histopathological features of first brain biopsy
(A) H&E-stained section of the first brain biopsy showed granulomatous inflammation with prominent neutrophilic infiltrates. (B) IHC testing highlighted scattered trophozoites (arrows) in areas showing a robust granulomatous inflammatory response. Degenerated amoebic cysts were identified on (C) Grocott's methenamine silver and on (D) IHC-stained tissue sections. Microphotographs provided by Infectious Diseases Pathology Branch (IDPB) laboratory at the Centers for Disease Control and Prevention
See this image and copyright information in PMC

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