Clinicopathological Study of Patients With C9ORF72-Associated Frontotemporal Dementia Presenting With Delusions.

BackgroundSeveral clinical studies point to a high prevalence of psychotic symptoms in frontotemporal dementia associated with C9ORF72 mutations, but clinicopathological studies addressing the association between C9ORF72 mutations and delusions are lacking.MethodSeventeen patients with pathologically proven frontotemporal lobar degeneration (FTLD) associated with C9ORF72 mutations were identified from Neurodegenerative Disease Brain Bank. Of the 17 cases with C9ORF72 mutation, 4 exhibited well-defined delusions. The clinical history, neurological examination, neuropsychological testing, neuroimaging analysis, and postmortem assessment of the patients with delusions were evaluated and compared with the other cases.ResultThe content of the delusions was mixed including persecution, infidelity, and grandiosity. All cases showed parkinsonism; voxel-based morphometry analysis showed greater precuneus atrophy in patients with delusions than those without delusions. All 4 had unclassifiable FTLD with TAR DNA-binding protein inclusions, with characteristics of both type A and type B. Three cases had additional τ pathology and another had α-synuclein pathology.ConclusionC9ORF72 carriers with well-defined delusions likely associated with additional pathologies and parietal atrophy in neuroimaging. Patients presenting with middle-aged onset of delusions should be screened for C9ORF72 mutations, especially if family history and parkinsonism are present