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 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