The role of the FTD-ALS associated C9orf72 expansion in suicide victims

Impulsive and aggressive traits are not only common features displayed by patients with behavioural variant frontotemporal dementia (bvFTD), they may well be the first clinical manifestations of the disease. In addition, suicidal behaviour has been postulated to be a symptom of bvFTD. A hexanucleotide repeat expansion in chromosome 9 open reading frame 72 (C9orf72) is the major genetic cause for familial bvFTD. During recent years, several genetic factors predisposing to suicide have been identified, but there are no previous studies analysing the role of the C9orf72 expansion in suicides. In the present study, we aimed to analyse the prevalence of the C9orf72 expansion in unselected suicide victims. The prevalence of the C9orf72 expansion was analysed in a cohort of 109 Finnish victims of suicide (mean age at death 46.1 years; range 18-86 years). The C9orf72 expansion was analysed from the post mortem blood samples. Results showed that no abnormal length C9orf72 expansions were detected in the study cohort. In conclusion, even though suicidal behaviour may be encountered in bvFTD patients, the C9orf72 expansion is not a common genetic finding in unselected suicide victims.