Variably protease‑sensitive prionopathy (VPSPr) is a rare sporadic human prion disease identified in the early 2000s. Unlike typical Creutzfeldt–Jakob disease, the abnormal prion protein in VPSPr exhibits heterogeneous sensitivity to protease digestion, producing unusual electrophoretic patterns. Clinically it presents with slowly progressive dementia, behavioral changes and motor symptoms and is invariably fatal.
Pathogenesis and Clinical Features
VPSPr arises without known PRNP mutations and appears to represent a distinct misfolded conformation of the prion protein. The pathological PrPSc in VPSPr has atypical glycoform ratios and shows varying resistance to proteinase K digestion, suggesting that multiple conformers coexist. Neuropathological examination reveals mild spongiform change, numerous kuru‑type plaques in the cerebellum and basal ganglia, and pronounced PrP deposition in the cerebral cortex and thalamus. The disease predominantly affects individuals with valine homozygosity at codon 129 of PRNP, although other genotypes can be involved. Clinical features begin with cognitive decline and psychiatric disturbances followed by speech difficulties, parkinsonism, cerebellar ataxia and pyramidal signs. Compared with sporadic Creutzfeldt–Jakob disease, VPSPr progresses more slowly, with a median disease duration of two to three years. Cerebrospinal fluid markers such as 14‑3–3 protein may be absent, and electroencephalograms lack periodic sharp wave complexes, complicating diagnosis. Brain magnetic resonance imaging often shows cortical ribboning and striatal hyperintensity on diffusion‑weighted images.
Known Cases and Distinctive Findings
VPSPr was first described in a series of patients reported in 2008 by investigators at the National Prion Disease Pathology Surveillance Center. Since then, dozens of cases have been recognized worldwide, accounting for roughly one to two percent of human prion diseases submitted to surveillance centers. Retrospective analyses suggest that some older cases of atypical Creutzfeldt–Jakob disease represented VPSPr but were misclassified due to a lack of biochemical testing. The protease‑sensitive nature of the pathological prion protein produces a characteristic ladder‑like pattern on western blots that distinguishes VPSPr from other prionopathies. There is no evidence of human‑to‑human transmission; all known cases have occurred sporadically. Definitive diagnosis relies on neuropathological examination and PrPSc typing. There is no effective treatment, and care remains supportive. Although rare, variably protease‑sensitive prionopathy expands the spectrum of human prion diseases and underscores the diversity of pathogenic prion conformations. Continued surveillance and biochemical characterization of atypical cases will improve understanding of its prevalence and pathogenesis. Related Terms: sporadic Creutzfeldt–Jakob disease, fatal familial insomnia, Gerstmann–Sträussler–Scheinker syndrome, prion protein, protease sensitivity