Early onset frontotemporal dementia with psychiatric presentation due to the C9ORF72 hexanucleotide repeat expansion: a case report

BACKGROUND Frontotemporal dementia (FTD) may present with psychiatric symptoms, usually together with neurological ones and in cases with a family history of dementia. We describe the case of an FTD behavioural variant with a psychiatric presentation and a normal neurological examination, due to a C9Orf72 gene mutation. CASE PRESENTATION The patient was a 57 years-old Caucasian woman with a recent onset of bizarre behaviours and mystic delusions. She had a negative clinical history for previous psychiatric disorders and treatments and this was her first admission to a Psychiatry Ward. A careful assessment was performed including, beyond psychiatric evaluation, the following: blood sampling, neurological examination (including electroencephalogram, electroencephalogram with zygomatic electrodes, Positron Emission Tomography, Cerebrospinal Fluid Analysis), carotid artery Doppler ultrasound, brain Magnetic Resonance Imaging - angio Magnetic Resonance Imaging. Blood sampling for the genetic assessment of mutations associated to primary dementias was performed as well: the genes investigated were FUS, C9Orf72, PSEN-1, PSEN-2. CONCLUSIONS Serological tests were negative, neurological examination was normal, instrumental examinations showed theta waves in the posterior temporal areas bilaterally and frontotemporal cortical atrophy bilaterally. The genetic assessment of mutations associated revealed she carried a GGGGCC hexanucleotide repeat expansion (at least 80 repeats) in C9Orf72 intron 1. Patients carrying the C9Orf72 mutation are likely to receive a psychiatric diagnosis (mainly mood disorder or schizophrenia) prior to correct diagnosis; this may be particularly problematic for those patients with no neurological signs to orientate diagnosis. Understanding the manner in which such FTD variant may present as a psychiatric syndrome, with a negative neurological examination, is essential to provide the best treatment for patients, as soon as possible, especially when the behavioural anomalies interfere with their care.