This 50-year old immunocompromised patient died after presenting with rapid cognitive decline and signs of brainstem dysfunction (cranial nerve deficits). MRI demonstrated multiple ring-enhancing cerebral and brainstem lesions. One of the lesions was biopsied.
What is you diagnosis based on Figures #1 to #3?
A. Toxoplasmosis
B. Acanthamoeba
C. HSV1/2
D. Coccidioidomycosis
Small collection of T. gondii organism, likely representing a bradyzoites disrupted during the process of performing the intraoperative cytology preparation (“squash prep”)
Lower power magnification showing a small area of parenchymal necrosis with two bradyzoites and many free tachyzoites.
Higher power magnification showing a small area of parenchymal necrosis with two bradyzoites and many free tachyzoites.
Answer: Toxoplasmosis
The intraoperative squash prep and tissue sections show bradyzoites (encysted organisms) and tachyzoites ( individual free organisms) of Toxoplasma gondii. These can be morphologically recognized on H&E. Immunohistochemical staining for the organism is very useful when there is a paucity of organisms or if there is extensive necrosis making it difficult to identify the tachyzoites.
T. gondii is a very successful parasite, infecting approximately 1/3 of the world’s human population. Cats (and other felidae) are definitive hosts, while humans and a wide variety of other warm-blooded animals are intermediate hosts.
In immunocompetent humans primary infection is most commonly asymptomatic to mildly symptomatic, and establishes lifelong latent infection. Reactivation of a previously latent infection occurs in the setting of immunocompromise. Primary or reactivated infection during pregnancy can result in severe fetal encephalitis.
Please see reference for additional information.
Reference(s) / additional reading:
Halonen SK, Weiss LM. Toxoplasmosis. Handb Clin Neurol. 2013;114:125-45. doi: 10.1016/B978-0-444-53490-3.00008-X. PMID: 23829904; PMCID: PMC4157368.
Schlüter D, Barragan A. Advances and Challenges in Understanding Cerebral Toxoplasmosis. Front Immunol. 2019 Feb 14;10:242. doi: 10.3389/fimmu.2019.00242. PMID: 30873157; PMCID: PMC6401564.
Dunay IR, Gajurel K, Dhakal R, Liesenfeld O, Montoya JG. Treatment of Toxoplasmosis: Historical Perspective, Animal Models, and Current Clinical Practice. Clin Microbiol Rev. 2018 Sep 12;31(4):e00057-17. doi: 10.1128/CMR.00057-17. PMID: 30209035; PMCID: PMC6148195.
Attias M, Teixeira DE, Benchimol M, Vommaro RC, Crepaldi PH, De Souza W. The life-cycle of Toxoplasma gondii reviewed using animations. Parasit Vectors. 2020 Nov 23;13(1):588. doi: 10.1186/s13071-020-04445-z. PMID: 33228743; PMCID: PMC7686686.
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