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Updated: Jul 11 2021

Toxoplasmosis (CNS)

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  • Snapshot
    • A 29-year-old male is brought to the emergency department by his male partner due to chronic headache and confusion. The patient is HIV positive, and his CD4+ count one month ago was 73 cells/μL. He has not been adherent to his antiretroviral and prophylactic therapy. An MRI of the head is shown. Enzyme linked immunoassay (ELISA) shows positive anti-toxoplasma IgG antibodies.
  • Introduction
    • Most common infection of the central nervous system in patients with AIDS
    • Caused by Toxoplasma gondii
      • an obligate intracellular protozoan
    • Infection in immunocompetent
      • usually asymptomatic
    • Infection in immunosuppressed (e.g., AIDS)
      • parasite reactivation → infection
      • CD4+ count < 100 cells/μL
      • encephalitis
        • ring-enhancing lesion on head imaging
      • retinochoroiditis
    • Extracerebral manifestations of toxoplasmosis
      • choroiretinitis
      • pneumonitis
  • Epidemiology
    • 30% risk of reactivation in immunocompromised (especially CD4+ count < 100 cells/μL)
      • in those not receiving prophylaxis or antiretroviral therapy
    • ~ 30% of the worldwide population is infected
  • Presentation
    • Symptoms
      • headache
      • fever
      • seizure
      • focal neurological deficit
      • confusion
      • flu-like symptoms
    • Physical symptoms
      • cervical lymphadenopathy
  • Evaluation
    • Head imaging
      • Head CT or head MRI
        • ring-enhancing lesion
        • MRI is more sensitive and preferred
    • Serology
      • testing for anti-toxoplasma IgM and IgG antibodies via ELISA
  • Differential
    • Brain abscess
    • CNS lymphoma
    • Metastatic cancer
    • Neurocysticercosis
  • Treatment
    • Medical
      • pyrimethamine + sulfadiazine + leucovorin
        • can replace sulfadiazine with clindamycin in those intolerant to sulfa-drugs
      • corticosteroids
        • only in those with mass effect
      • anticonvulsants
        • only in those presenting with seizures
    • Special considerations
      • HIV
        • CD4+ Count < 100 mm3
          • for patients with a past medical history of HIV with severe immunosuppression (CD4 <100 cells/µL), focal neurologic findings, and ring-enhancing lesions on head imaging, the next step in management is empiric treatment for toxoplasma encephalitis with pyrimethamine-sulfadiazine for 10-14 days.
            • get follow-up head imaging after 10-14 days. If the patient fails to improve clinically or the size of the lesion does not change, the next step would be a biopsy of the lesion.
  • Prevention, Prognosis, and Complications
    • Prevention
      • primary prophylaxis with TMP-SMX in those with a CD4+ count < 100 cells/μL
        • alternative
          • atovaquone +/- pyrimethamine (+ leucovorine)
          • dapsone + pyrimethamine + leucovorine
      • safe water use
      • frequently change the cat litter
      • thoroughly clean fruits, vegetables, and meats
      • don't drink unpasteurized goat milk
    • Prognosis
      • severe in immunocompromised
        • ↑ mortality
    • Complications
      • maternal transmission
      • reactivation mostly occurs in the immunocompromised
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