Psychosis and hallucinations in frontotemporal dementia with the C9ORF72 Mutation: A detailed clinical cohort

OBJECTIVE:: To specify the presenting symptoms and clinical course of patients with frontotemporal dementia (FTD) and chromosome 9 open reading frame 72 (C9ORF72) repeat expansion. BACKGROUND:: The 2011 discovery of the C9ORF72 repeat expansion causing familial FTD and amyotrophic lateral sclerosis has permitted retrospective evaluation of potential defining clinical characteristics that may distinguish carriers of the C9ORF72 mutation from other patients with FTD. Prior reports identified a subset of patients with FTD who had an unusually high prevalence of psychosis, although their specific symptoms had not yet been fully described. METHODS:: From a cohort of 62 patients with FTD, we conducted a retrospective chart review of 7 patients who had C9ORF72 mutations on genetic testing, and 1 untested sibling of a C9ORF72 carrier. RESULTS:: Detailed histories revealed a higher prevalence of psychosis, including visual and auditory hallucinations and delusions, in the 8 C9ORF72 carriers than in our patients with sporadic FTD. CONCLUSIONS:: This cohort confirms and adds clinical details to the reports of a high prevalence of psychotic phenomena in patients who have C9ORF72 mutations as well as FTD or amyotrophic lateral sclerosis.