Autopsied case of sporadic Creutzfeldt–Jakob disease classified as MM1+2C-type

We encountered an autopsy case of sporadic Creutzfeldt-Jakob disease (CJD) pathologically classified as MM1+2C-type, where Western blot analysis of prion protein (PrP) mainly showed type-1 scrapie PrP (PrP^Sc) but also, partially, mixed type-2 PrP^Sc. A Japanese woman complained of visual disorder at the age of 86 years and then showed disorientation and memory disturbances. Magnetic resonance imaging (MRI) showed cerebral cortical hyperintensity on diffusion-weighted images. The patient died 2 months after the onset of symptoms; her condition did not reach the akinetic mutism state and periodic sharp-wave complexes on electroencephalography and myoclonus were not recognized. The brain weighed 1100 g and neuropathological examination showed extensive fine vacuole-type spongiform changes in the cerebral cortex. In some cortical regions, large confluent vacuole-type spongiform changes were also present. Gliosis and hypertrophic astrocytosis were generally mild, and tissue rarefaction of the neuropil and neuronal loss were not apparent. PrP immunostaining showed diffuse synaptic-type PrP deposition in the cerebral gray matter, but some regions with large confluent vacuoles showed perivacuolar-type deposition. We speculated, based on the clinicopathological findings and previous reports, that most MM1-type sporadic CJD cases may be associated with type-2 PrP^Sc, at least partially, within certain regions of the cerebrum.