%0 Journal Article
%T Clinical Manifestations.
%A Boer SCM
%A Krudop WA
%A Gossink FT
%A Oudega ML
%A Kerssens CJ
%A Dols A
%A van Ruissen R
%A Lee SJ
%A Pijnenburg YAL
%J Alzheimers Dement
%V 19
%N 0
%D 2023 Dec
%M 39112069
%F 16.655
%R 10.1002/alz.080018
%X <B>BACKGROUND: </B>The C9orf72-repeat expansion (C9RE) is the most prevalent genetic cause of frontotemporal dementia (FTD). Since its discovery, studies have shown that both family history (FH) and medical history of FTD patients carrying a C9RE are often not only positive for dementia, but also for psychiatric disorders and late-onset behavioural change. Conversely, finding a C9RE carrier in a primary psychiatric disorder (PPD) cohort is rare. These findings justify clinicians to test for the C9RE, regardless of FH, when diagnosing a patient with FTD but not to screen for C9REs in PPD cohorts. It is unknown what the frequency is of C9RE in cases presenting with late-onset behavioural change. Therefore, we investigated the diagnostic value of screening for C9RE in cases with late-onset behavioural change.<BR><B>METHODS: </B>Patients with late-onset (>45years) behavioural change referred to the Alzheimer Center Amsterdam between 2011 and 2023, that received a baseline diagnosis of FTD or non-FTD were included. Genetic screening was performed and mutation carriers other than C9RE were excluded. The cohort was devided in C9RE-carriers and non-carriers. FH data was retrieved. Positive FH (FH+) was defined as having a first-degree relative with dementia or psychiatry, negative FH (FH-) without a first-degree relative with dementia or psychiatry. Distribution of FH(+/-) between C9RE-carriers and non-carriers was studied. Within the C9RE-carriers, distribution of FH between FTD and non-FTD diagnosis was measured. Distributions were compared using chi-squared tests.<BR><B>RESULTS: </B>A total of n = 344, of which 16,2% C9RE-carriers, were included. Of the C9RE-carriers, 66.7% had a FH+ versus 35.7% of the non-carriers (p = 4.36e-05). Within the C9RE-carriers group, n = 34 cases received a FTD diagnosis of which n = 20 had a FH- (58.5%) versus n = 20 cases receiving a non-FTD diagnosis of which n = 14 (70%) having a FH- (p-value = 0.596, table 1).<BR><B>CONCLUSIONS: </B>Within a cohort of late-onset behavioural change, 14 cases (4.2% of total cohort) received a non-FTD diagnosis, had a negative FH for dementia and psychiatry but turned out to have a C9RE. This shows late-onset behavioural change is enriched with C9RE, regardless of FH or baseline diagnosis, and suggests that screening for C9RE is of both diagnostic and prognostic value in late-onset behavioural disorders.