A Case with Early Onset Alzheimer's Disease, Frontotemporal Hypometabolism, ApoE Genotype ϵ 4/ ϵ 4 and C9ORF72 Intermediate Expansion: A Treviso Dementia (TREDEM) Registry Case Report

We report the case of a woman firstly referred to our Memory Clinic at the age of 61, following the development of cognitive complaints and difficulties in sustained attention. The investigation that was performed showed: predominant executive dysfunctions at the neuropsychological evaluation, with mild, partial and stable involvement of the memory domain; cortical and subcortical atrophy with well-preserved hippocampal structures at MRI; marked fronto-temporal and moderate parietal hypometabolism from 18 F-FDG PET study with a sparing of the posterior cingulate and precuneus; positivity of amyloid-β at 18 F-Flutemetamol PET; an hexanucleotide intermediate repeats expansion of C9ORF72 gene (12//38 repeats) and ApoE genotype ϵ4/ϵ4. The patient was diagnosed with probable early onset frontal variant of Alzheimer's disease (AD), presenting with a major executive function impairment. The lack of specific areas of brain atrophy, as well as the failure to meet the clinical criteria for any frontotemporal dementia, drove us to perform the aforementioned investigations, which yielded our final diagnosis. The present case highlights the need to take into consideration a diagnosis of frontal variant of AD when the metabolic and the clinical picture are somehow dissonant.