A 35-year-old HIV-positive patient (CD4 count 28 cells/μL) presents with 3 weeks of progressive cognitive decline, headache, and focal neurological signs. MRI brain shows multiple ring-enhancing lesions with mass effect in the basal ganglia and thalamus. CSF PCR is pending. What is the most appropriate empiric therapy while awaiting results?
- A Empiric treatment for toxoplasma encephalitis: pyrimethamine + sulfadiazine + folinic acid ✓
- B Empiric treatment for CNS lymphoma: high-dose methotrexate
- C Empiric treatment for cryptococcal meningitis: liposomal amphotericin B + flucytosine
- D Initiate ART immediately and observe lesions for 2 weeks before specific treatment
Explanation
Ring-enhancing lesions in an AIDS patient with CD4 <100 cells/μL are Toxoplasma gondii encephalitis until proven otherwise (~50% of cases). Standard empirical approach is to treat for toxoplasmosis (pyrimethamine 200 mg loading then 50–75 mg/day + sulfadiazine 4–6 g/day in divided doses + folinic acid 10–25 mg/day to prevent bone marrow suppression). Clinical and radiological response is expected within 2 weeks — lack of response suggests CNS lymphoma or other diagnosis. Radiological criteria favouring toxoplasmosis over PCNSL include multiple lesions, peripheral location, and serology (positive anti-Toxoplasma IgG). Cryptococcal meningitis typically presents as non-enhancing basilar meningitis, not ring-enhancing masses.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.