[Auditory hallucination as an initial sign of frontotemporal dementia]

A 58-year-old right-handed man presented with a 9-year history of stereotyped behaviors and auditory hallucinations. At 49 years of age, he began to complain about auditory hallucinations that said offensive things about him, and around the same time, he began exhibiting stereotyped behaviors. For example, he traveled the same long route from his office to home every evening. Disinhibitory behavior occurred at 53 years of age, and he was forced to retire at 54 years of age. After retirement, the patient stayed in bed or showed a stereotyped behavior of repeatedly going to a nearby shrine every day. The complaint of auditory hallucinations disappeared around this time. At 57 years of age, he began using a day service, and soon after, several stereotyped behaviors appeared in this setting as well. Brain magnetic resonance imaging at 59 years of age showed severe atrophy and knife-blade-like appearance in the bilateral temporal poles. A clinical diagnosis of frontotemporal dementia (FTD) was made based on the neurobehavioral, neuropsychological, and neuroimaging findings. FTD patients have been reported to show hallucinations very rarely. However, recent studies have reported that frontotemporal lobar degeneration (FTLD) patients with ubiquitin-positive and transactive response-DNA-binding protein-43 (TDP-43)-positive pathologies (FTLD-U-TDP) and FTD patients with progranulin gene mutations often develop hallucinations. The current patient may belong to this group of patients with similar neuropathological and molecular biological bases.