Massive Intracranial Lesion in an AIDS Patient: Diagnostic Challenge Between Brain Tumor and Toxoplasmic Encephalitis Resolved by Empirical Therapy.

Background: Human immunodeficiency virus (HIV)-associated cerebral toxoplasmosis is the most frequent cause of ring-enhancing brain lesions in acquired immune deficiency syndrome (AIDS) patients but is often misdiagnosed as neoplasm due to overlapping clinical and radiological features. Seronegative examinations further complicate diagnosis, risking fatal delays in treatment. Case Presentation: A 32-year-old male with undiagnosed HIV presented with right hemiparesis, dysarthria, and headache. Magnetic resonance imaging (MRI) revealed a 38×54 mm ring-enhancing left frontoparietal mass with significant edema, midline shift, and ventricular compression, initially suggestive of glioblastoma. HIV serology confirmed infection. Toxoplasma antibodies, nucleic acid test and next-generation sequencing were all negative. Despite 17 days of antiretroviral therapy and sulfamethoxazole-trimethoprim prophylaxis, he deteriorated to coma with lesion progression on repeat MRI. Empirical anti-toxoplasma therapy was initiated. Within one week, consciousness and speech improved. At 6 weeks, MRI showed reduced lesion size and edema, and right limb strength partially recovered, enabling discharge. Conclusion: This case illustrated that seronegative Toxoplasmic encephalitis may mimic aggressive neoplasms radiologically and clinically in advanced AIDS. Empirical anti-toxoplasma therapy should be considered a prioritized intervention over invasive diagnostics for ring-enhancing lesions in severely immunocompromised patients, particularly when brain biopsy is high-risk or contraindicated, even in seronegative cases.