An autopsy case of MV 2K + C subtype of Creutzfeldt–Jakob disease

Methionine/valine (MV) 2 type of sporadic Creutzfeldt–Jakob (sCJD) is divided into three subtypes based on neuropathological criteria: MV2‐kuru (MV2K), MV2‐cortical (MV2C), and MV2K + C, exhibiting the co‐occurrence of these two pathological features. We report an autopsy case of MV2K + C subtype of sCJD. A 46‐year‐old Japanese man began to make mistakes at work. Two months later, he gradually developed gait instability. The initial neurological examination revealed limb ataxia and myoclonus. Diffusion‐weighted images (DWI) showed a hyperintensity in the right frontal cortex, basal ganglia, and thalamus. Ten months after the onset of disease, he fell into akinetic mutism. He died at 47 years of age, 12 months after the initial presentation. Pathological investigation revealed microvacuolation and confluent vacuoles in the cerebral cortex. In the basal ganglia and thalamus, there was severe neuronal loss and gliosis with mild spongiform change. Kuru plaques were found within the cerebellum. Prion protein (PrP) immunostaining revealed synaptic, perivacuolar, perineuronal, and plaque‐like deposits in the cerebral cortex. There were synaptic and plaque‐like PrP deposits in the basal ganglia, thalamus, and granular cell layer of the cerebellum. In these areas, plaque‐like deposits mainly consisted of small deposits, whereas plaque‐like deposits in the cerebral cortex consisted both of coarse granular and small deposits. Analysis of the PrP gene showed no pathogenic mutations, and Western blot examination revealed a mixture of type 2 and intermediate‐type PrP. The progressive cognitive decline and ataxia in addition to the hyperintensity in the basal ganglia and/or thalamus on DWI are the basis for clinical diagnosis of MV2. The severe gliosis in the basal ganglia and various morphologies of plaque‐like deposits that differ by the region may be characteristic of MV2K + C. Detailed neuropathological examination together with Western blot analysis is important to collect more cases for elucidating the pathogenesis of MV2K + C.