Ring-enhancing brain lesions in a patient with advanced retroviral disease

The patient is a 30-year-old man who was recently diagnosed with HIV infection and has a CD4 count of 30 cells/mm3. He presented with a one-week history of intermittent fever and right-sided body weakness, and upon examination, was found to have right hemiparesis. There were no other features of opportunistic infections noted. A contrast-enhanced computed tomography (CT) scan of the brain revealed a hypodense lesion with a rounded enhancing rim in the left basal ganglia, measuring 3 x 3 x 2.5 cm. The lesion was associated with marked deep white matter oedema, causing effacement of the lateral and third ventricles, as well as a slightly dilated temporal horn of the right lateral ventricle. The left cerebral sulci were also effaced (Figure 1).