Frontal variant of Alzheimer’s disease masquerading as behavioural-variant frontotemporal dementia: a case study comparison

The current clinical diagnostic criteria for Alzheimer’s disease (AD) recognize an atypical, non-amnestic presentation of AD, characterized by prominent executive dysfunction. Increasing evidence, however, indicates that the clinical phenotype of this so-called “frontal-variant” of AD (fv-AD) includes behavioral symptoms and deficits in social cognition, together with disproportionate frontal lobe atrophy. As these features resemble those characteristic of behavioral-variant frontotemporal dementia (bvFTD), differential diagnosis can be challenging. Here, we report a case of fv-AD who met clinical diagnostic criteria bvFTD, but had in vivo amyloid neuroimaging evidence of AD pathology. We compare this case against two individuals who were clinically diagnosed with bvFTD and early-onset AD, with in vivo amyloid neuroimaging confirmation of pathology. We highlight the challenges in differential diagnosis by contrasting their behavioral, cognitive and structural neuroimaging findings.