A 39-year-old man with a recent diagnosis of HIV infection was admitted to this hospital with fever and bizarre, nihilistic delusions, including statements that he had died. A diagnostic procedure was performed.

A 32-year-old woman had seizures since childhood, myoclonus, and recent cognitive decline. Family members had an autosomal-dominant pattern of neurologic disease. Diagnostic testing was performed. Cognitive decline continued; the patient died 2 years later. An autopsy was performed.

An 87-year-old woman with a history of dementia was admitted to this hospital because of a seizure. A diagnosis of possible Alzheimer's disease had been made 4 years earlier; at baseline, she recognized only her husband and children. On examination, she was unresponsive. Magnetic resonance imaging scans of the brain revealed T₂-weighted hyperintensities in the white matter involving both cerebral hemispheres, as well as innumerable small foci of susceptibility-weighted artifact at the cortical–subcortical junction. Despite a temporary improvement after treatment, she died of pneumonia a few days later. An autopsy was performed.

A 69-year-old woman presented to this hospital because of a 2-month period of increasing apathy, confusion, and depression. She had a history of connective-tissue disease and idiopathic thrombocytopenic purpura. Ten days before admission, a magnetic resonance image of the brain was obtained, which was abnormal.