Frontotemporal dementia (FTD) usually begins in middle age with neuropsychiatric symptoms. The development of disinhibition, socially inappropriate behaviour, emotional disengagement, repetitive behaviour and poor insight can lead to FTD being misdiagnosed as psychosis but the true prevalence of psychosis in people with FTD is unclear. A U.S. study of 109 people compared those with FTD to those with Alzheimer's. Among the FTD patients only 2.3% had delusions, only half of whom had paranoid ideas and no FTD patients had hallucinations. By contrast 17.4% of the Alzheimer's patients experienced delusions and paranoia. A review of other studies also failed to establish a significant association between FTD and psychosis.
Mendez, Mario F. ... [et al] - Psychotic symptoms in frontotemporal dementia: prevalence and review Dementia and geriatric cognitive disorders 2008, 25: 206-211