A 24-Year-Old Man With a Left Frontal Brain Mass.

A healthy 24-year-old man presented with 1 week of headache, gait imbalance, and coordination difficulties. His mother reported that he had experienced personality changes. He denied any fevers, chills, night sweats, or weight loss. He reported smoking marijuana and denied tobacco and intravenous drug use. He is sexually active, with multiple male partners. On examination, he was alert and oriented, with a temperature of 36.3°C, blood pressure of 131/90 mm Hg, heart rate of 94/min, respiratory rate of 18/min with pulse oximetry of 98% on ambient air, and a body mass index of 28.1 (calculated as weight in kilograms divided by height in meters squared). Neurologic examination was significant for hyperreflexia in all extremities, bilateral shoulder weakness, and right-sided pronator drift. Laboratory results showed a white blood cell count of 3600/μL (73.5% neutrophils, 16.4% lymphocytes, 7.8% monocytes, 1.4% eosinophils, 0.6% basophils); the remainder of the complete blood cell count and comprehensive metabolic profile was unremarkable. The result of a human immunodeficiency virus (HIV) type 1 antibody test was positive, and CD4 cell count was 73/mm3. Results of serologic testing for Toxoplasma gondii IgG were negative. Computed tomography (CT) imaging of the brain showed a left caudate nucleus and lentiform nucleus lesion with mass effect on the left lateral ventricle (Figure, left panel). Fluid-attenuated inversion recovery magnetic resonance imaging (MRI) of the brain confirmed the presence of an aggressive mass lesion extending through the corpus callosum (Figure, right panel). CT of the chest, abdomen, and pelvis and spinal MRI were unremarkable. Figure. Left, Computed tomography scan of the brain, axial view, with contrast. Right, Fluid-attenuated inversion recovery magnetic resonance imaging of the brain, axial view.