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.