Variably protease sensitive prionopathy
Variably protease sensitive prionopathy (VPSPr) is a very rare type of sporadic human prion disease that was first described in 2008.
Clinical presentation is varied, but most patients demonstrate a combination of:
- progressive neuropsychiatric features: dementia and psychosis 1-3
- progressive motor features: ataxia and parkinsonism 1-3
- progressive aphasia 1-3
It is thought that many patients have previously been misdiagnosed as normal pressure hydrocephalus, Parkinson disease, dementia with Lewy bodies, or frontotemporal dementia, due to the overlap with the clinical features of VPSPr 3.
Neuropathologically, VPSPr is characterised by spongiform degeneration of the cerebral neocortex, basal ganglia, and thalamus, with relative sparing noted in infratentorial structures 1-3. Unlike all other sporadic prion diseases which are all associated with prion protein (PrP) that is resistant to treatment with proteases, the PrP in VPSPr is somewhat sensitive to these enzymes, making the condition neuropathologically-unique compared to these other prion diseases 1-3. Furthermore, it has been established that VPSPr has only a limited potential for human-to-human transmission 4.
Radiographic features are non-specific in VPSPr. In available case series-level evidence, MRI has been reported to demonstrate cerebral atrophy 1-3. Notably, and unlike other prion diseases, patients have not demonstrated any regions of high or abnormal diffusion signal on DWI 1-3.
Treatment and prognosis
Currently (as of August 2017), there is no treatment currently available for VPSPr so supportive symptomatic management is recommended 3. In regards to prognosis, the mean duration of symptoms is reported to be approximately 20 months before death, notably longer than other prion diseases such as Creutzfeldt-Jakob disease 1.
History and etymology
The disease was first recognised by Pierluigi Gambetti, an Italian-American neuropathologist and previous director of the National Prion Disease Pathology Surveillance Center, and his colleagues in 2008 1.
- 1. Gambetti P, Dong Z, Yuan J, Xiao X, Zheng M, Alshekhlee A, Castellani R, Cohen M, Barria MA, Gonzalez-Romero D, Belay ED, Schonberger LB, Marder K, Harris C, Burke JR, Montine T, Wisniewski T, Dickson DW, Soto C, Hulette CM, Mastrianni JA, Kong Q, Zou WQ. A novel human disease with abnormal prion protein sensitive to protease. Annals of neurology. 63 (6): 697-708. doi:10.1002/ana.21420 - Pubmed
- 2. Zou WQ, Puoti G, Xiao X, Yuan J, Qing L, Cali I, Shimoji M, Langeveld JP, Castellani R, Notari S, Crain B, Schmidt RE, Geschwind M, Dearmond SJ, Cairns NJ, Dickson D, Honig L, Torres JM, Mastrianni J, Capellari S, Giaccone G, Belay ED, Schonberger LB, Cohen M, Perry G, Kong Q, Parchi P, Tagliavini F, Gambetti P. Variably protease-sensitive prionopathy: a new sporadic disease of the prion protein. Annals of neurology. 68 (2): 162-72. doi:10.1002/ana.22094 - Pubmed
- 3. Gambetti P, Puoti G, Zou WQ. Variably protease-sensitive prionopathy: a novel disease of the prion protein. Journal of molecular neuroscience : MN. 45 (3): 422-4. doi:10.1007/s12031-011-9543-1 - Pubmed
- 4. Diack AB, Ritchie DL, Peden AH, Brown D, Boyle A, Morabito L, Maclennan D, Burgoyne P, Jansen C, Knight RS, Piccardo P, Ironside JW, Manson JC. Variably protease-sensitive prionopathy, a unique prion variant with inefficient transmission properties. Emerging infectious diseases. 20 (12): 1969-79. doi:10.3201/eid2012.140214 - Pubmed
Neurodegenerative diseases are legion and their classification just as protean. A useful approach is to divide them according to underlying pathological process, although even using this schema, there is much overlap and thus resulting confusion.
neurodegenerative MRI brain (an approach)
- measurements and ratios
- midbrain to pons area ratio (for PSP)
- Magnetic Resonance Parkinsonism Index (MRPI) (for PSP)
- frontal horn width to intercaudate distance ratio (FH/CC) (for Huntington disease)
- intercaudate distance to inner table width ratio (CC/IT) (for Huntington disease)
- scoring systems
- measurements and ratios
- typical/classical Alzheimer disease
- variant (e.g. posterior cortical atrophy)
- chronic traumatic encephalopathy (CTE)
- corticobasal degeneration
- frontotemporal lobar degeneration (FTLD) (not all are tau)
- Pick disease
- progressive supranuclear palsy (PSP)
- Alzheimer disease
- cerebral amyloidosis
- spinocerebellar ataxias
- Huntington disease
- hereditary spastic paraplegia
- amyotrophic lateral sclerosis (ALS)
- clinically unclassifiable parkinsonism (CUP)
- Unverricht-Lundborg disease
- prion diseases (not always included as neurodegenerative)