Extensive cortical spongiform changes with cerebellar small amyloid plaques: The clinicopathological case of MV2K+C subtype in Creutzfeldt‐Jakob disease

We report a clinical case report of the MV2K+C subtype of sporadic Creutzfeldt‐Jakob disease (sCJD). The patient was a 72‐year‐old woman who exhibited progressive dementia over the course of 22 months. Diffusion‐weighted MRI during this period showed abnormal hyperintensity in the cerebral cortex in the early stage. The clinical course was similar to that of previously reported patients with the MV2K or MV2K+C subtype of sCJD. However, histopathological examination revealed unique features: severe extensive spongiform changes with perivacuolar deposits in the cerebrum and basal ganglia, plaque‐like PrP deposits in the cerebrum, and only mild changes in the cerebellum with small amyloid plaques (∼20 μm in diameter), smaller than those in the MV2K subtype or variant CJD (40–50 μm in diameter). Molecular analysis showed a methionine/valine heterozygosity at codon 129 and no pathogenic mutation in the PrP gene (PRNP). Western blot analysis of the protease‐resistant PrP (PrPSc) in the right temporal pole revealed the type 2 pattern, which is characterized by a single unglycosylated band, in contrast to the doublet described for the typical MV2 subtype of sCJD. The other intermediate band might exist in the cerebellum with kuru plaques. Therefore, small amyloid plaques in the cerebellum can be crucial for MV2K+C subtype.