From slowly progressive amnesic syndrome to rapidly progressive Alzheimer disease.

A 57-year-old woman had a neuropsychologically documented 5-year history of a slowly progressive amnesic syndrome followed by a 1-year history of rapidly progressive dementia. There was no family history of dementia. Magnetic resonance imaging failed to show a structural basis, electroencephalography failed to show changes of Creutzfeldt-Jakob disease, and cerebrospinal fluid examination was normal. A diagnosis of Alzheimer disease was confirmed by brain biopsy. The abrupt change in disease course was unique but suggested probable overlap between posited subtypes of Alzheimer disease.