Clinical Reasoning: An Unexpected Response to Therapy in a Patient With HIV and Focal Seizures.

We present the case of a 23-year-old right-handed man who presented to an emergency department in Lusaka, Zambia with new-onset headaches and focal seizures. He was on combination antiretroviral therapy (cART) for HIV and had been started on anti-tuberculous therapy at his local clinic two weeks prior to presentation based on chest x-ray findings. On examination, he had subtle weakness and hyperreflexia in his left upper extremity. The remainder of the neurological examination was normal. Brain computed tomography (CT) scan revealed a single, ring-enhancing heterogenous mass in the right posterior parietal lobe with marked vasogenic edema. His lab results revealed severe virologic and immunologic failure, and CSF analysis was unremarkable. He was empirically managed as CNS TB. Two months later, his symptoms worsened and he developed new neurologic deficits despite adherence to cART and TB treatment. Repeat imaging subsequently revealed progression of his underlying CNS process with multiple brain abscesses present, and subsequent investigations revealed an unusual cause of these lesions. In this case, we review the differential diagnosis for space-occupying lesions in the context of poorly controlled HIV infection. In particular, we highlight the approach to these patients in resource-limited settings in the context of diagnostic limitations and highlight the importance of considering the local epidemiology of neurological infections. Finally, this case demonstrates the need to maintain a wide differential diagnosis and a close monitoring plan for prompt re-evaluation of empiric diagnoses when response to empiric therapy is unexpected.