A young man with progressive language difficulty and early-onset dementia

A man in his late 40s presented with cognitive decline characterized by gradually increasing difficulty expressing his thoughts and ideas. His family noted word-finding difficulty, especially with the names of people, but no problems with his memory for recent events. Initial workup findings were unremarkable, but during the course of the next decade left anterior temporal atrophy was noted on magnetic resonance imaging and the patient developed increasing reasoning difficulty, apathy, and disinhibition. Several degenerative causes were considered. The patient died 22 years after symptom onset, and the final diagnosis was confirmed at autopsy.