Table 1. Comparison of features in familial dementias: frontotemporal lobar degeneration, Alzheimer's disease and prion disease.

Genetic mutation	Presenting syndrome	Behavioral and cognitive features	Parkinsonism	Motor neuron disease	Other clinical features	Neuroimaging features
GRN	bvFTLD PNFA CBS	Behavioral syndrome (apathy, sweet tooth, etc.), executive dysfunction, episodic memory impairment, aphasia, parietal lobe dysfunction	+	Rare	Features of CBS can be present	Often asymmetrical frontal, temporal and parietal lobe atrophy
MAPT	bvFTLD CBS PSP	Behavioral syndrome (disinhibition, inappropriate social behaviour, etc.), executive dysfunction, decreased speech, anomia	+	−	Features of CBS or PSP can be present	Bilateral frontotemporal lobar atrophy
VCP	bvFTLD	Behavioral syndrome, executive dysfunction	−	−	Inclusion body myopathy and Paget's disease	A few reports of frontotemporal lobar atrophy
CHMP2B	bvFTLD	Behavioral syndrome (apathy, restlessness, aggression etc.), executive dysfunction, decreased speech, can have early parietal impairment	−	Rare	None	Generalized atrophy
Chr 9 FTD- MNDa	bvFTLD MND	Behavioral syndrome, executive dysfunction	−	+	None	Single report of frontal lobe atrophy sparing posterior regions
APP, PS1, PS2​15	AD (i.e. amnestic presentation) Atypical ADb	Episodic memory impairment initially then global impairment	Rare	−	Myoclonus or seizures can occur. Spastic paraparesis is seen rarely in PS1.	Presymptomatic medial temporal lobe atrophy spreading to diffuse neocortical areas
PRNP​16	Dementia with neurological signs	Highly heterogenous, ranging from rapidly progressive dementia with myoclonus and ataxia, similar to classical CJD, to much more slowly progressive syndromes involving episodic memory, executive dysfunction, dyspraxia	+	Rare	Ataxia, myoclonus, seizures, chorea, or dystonia	Generalized cerebral and cerebellar atrophy typical. Rapidly progressive clinical syndromes can be associated with high signal in the caudate and putamen on T2-weighted MRI

^aA locus on chromosome 9p has been associated with FTD-MND but the abnormal gene has yet to be found.

^bRarely, a prominent behavioral phenotype similar to bvFTLD is seen in patients with PS1 mutations.

Abbreviations: AD, Alzheimer's disease; APP, amyloid precursor protein; bvFTLD, behavioral variant frontotemporal lobar degeneration; CBS, corticobasal syndrome; CHMP2B, chromatin-modifying protein 2B; Chr 9 FTD-MND, chromosome 9-associated frontotemporal dementia with motor neuron disease; CJD, Creutzfeldt-Jakob disease; GRN, progranulin, MAPT, microtubule-associated protein tau; PNFA, progressive nonfluent aphasia; PRNP, prion protein, PS1, presenilin 1; PS2, presenilin 2; PSP, progressive supranuclear palsy, VCP, valosin-containing protein; +, can be present; −, absent