Pandora's Box: Not Every Box Unleashes Harm - Brain Biopsy Unmasks Cerebral Nocardiosis and Redirects Therapy in a Woman with Advanced HIV and Pulmonary Tuberculosis

Cerebral nocardiosis is a rare cause of brain abscess in people with advanced human immunodeficiency virus infection and is easily mistaken for cerebral toxoplasmosis or tuberculoma. We report a woman in her mid-thirties with advanced human immunodeficiency virus infection (CD4+ T-cell count 10 cells/mm³), poor adherence to antiretroviral therapy and rifampicin-sensitive pulmonary tuberculosis, who presented with headache and vomiting. Magnetic resonance imaging showed multiple ring-enhancing lesions with an eccentric target sign, Toxoplasma gondii IgG was reactive, cerebrospinal fluid studies identified no pathogen, and positron emission tomography–computed tomography argued against primary central nervous system lymphoma. She was treated empirically for cerebral toxoplasmosis alongside anti-tuberculosis and antiretroviral therapy, with initial improvement. During corticosteroid taper she deteriorated with right upper limb weakness, focal motor seizures and radiological progression, initially attributed to immune reconstitution inflammatory syndrome. After three non-diagnostic cerebrospinal fluid examinations, stereotactic biopsy of the left parietal lesion showed branching filamentous organisms, and 16S ribosomal RNA sequencing identified Nocardia farcinica. Intravenous meropenem and amikacin, added to high-dose trimethoprim–sulfamethoxazole, produced sustained clinical and radiological improvement. In advanced human immunodeficiency virus infection, ring-enhancing brain lesions that progress despite appropriate empirical therapy should prompt early tissue diagnosis with molecular sequencing, and immune reconstitution inflammatory syndrome should remain a diagnosis of exclusion.