[Genetic Creutzfeldt-Jakob disease with a glutamate-to-lysine substitution at codon 219 (E219K) in the presence of the E200K mutation presenting with rapid progressive dementia following slowly progressive clinical course].

A 57-year-old man developed rapidly progressive dementia and a gait disturbance over 4 months. The patient had a slowly progressive executive dysfunction and speech problems for 4 years and was previously monitored in our outpatient clinic following a diagnosis of frontotemporal dementia. Diffusion-weighted MRI revealed high signal intensities in the right caudate nucleus and the bilateral cortices. Cerebrospinal fluid analysis showed increased levels of the 14-3-3 and total tau proteins. Periodic synchronous discharge was not evident on an electroencephalogram. Prion protein gene analysis identified a glutamate-to-lysine substitution at codon 219 (E219K) in the presence of the E200K mutation, leading to a genetic diagnosis of genetic Creutzfeldt-Jakob disease (CJD). The E219K polymorphism found on the allele of the E200K mutation may have influenced the characteristic clinical course of our patient that differed from that of typical E200K genetic CJD.