Cerebral toxoplasmosis in HIV — DTM&H MCQ

Correct answer: D — Empirical pyrimethamine, sulfadiazine, and folinic acid

The correct answer is D, empirical pyrimethamine, sulfadiazine, and folinic acid. Multiple ring-enhancing lesions on CT in a patient with advanced HIV (CD4 50 cells/uL) presenting with headache, confusion and focal neurology is the classic picture of cerebral toxoplasmosis, the commonest cause of focal CNS mass lesions at this level of immunosuppression. UK and international HIV guidance recommends starting empirical anti-toxoplasma therapy immediately without waiting for biopsy, because clinical and radiological improvement within 10 to 14 days effectively confirms the diagnosis while avoiding the delay and morbidity of neurosurgery. Folinic acid is co-prescribed to offset pyrimethamine-induced bone marrow suppression. Steroids are withheld unless there is life-threatening mass effect, as they can mask the diagnostic response to antimicrobial treatment and may worsen unrecognised CNS lymphoma. Why the other options are wrong: B. Brain biopsy for definitive diagnosis: reserved for cases failing to respond to a two-week empirical trial, not first-line, given the procedural risk in a critically unwell, immunosuppressed patient. A. Dexamethasone and urgent neurosurgical referral: steroids obscure the response to empirical treatment and there is no indication here for surgical decompression as the primary intervention. E. High-dose IV aciclovir for 21 days: treats HSV encephalitis, which typically causes temporal lobe changes and diffuse encephalopathy rather than multiple ring-enhancing lesions. C. Empirical antituberculous therapy: CNS tuberculomas are a differential but far less likely than toxoplasmosis with this classic multi-lesion ring-enhancing pattern at CD4 50, and would not be the first empirical choice. Key point: In advanced HIV with multiple ring-enhancing brain lesions, start empirical anti-toxoplasma therapy (pyrimethamine, sulfadiazine, folinic acid) and reassess clinically and radiologically at two weeks before considering biopsy.

Reference: HIV i-Base, Treatment Guide: Toxoplasmosis (Section 5.11, OIs and Coinfections), https://i-base.info/ttfa/5-ois-and-coinfections/11-toxoplasmosis/