RT Book, Section A1 Prusiner, Stanley B. A1 Miller, Bruce L. A2 Jameson, J. Larry A2 Fauci, Anthony S. A2 Kasper, Dennis L. A2 Hauser, Stephen L. A2 Longo, Dan L. A2 Loscalzo, Joseph SR Print(0) ID 1184194039 T1 Prion Diseases T2 Harrison's Principles of Internal Medicine, 20e YR 2018 FD 2018 PB McGraw-Hill Education PP New York, NY SN 9781259644016 LK accessmedicine.mhmedical.com/content.aspx?aid=1184194039 RD 2024/10/13 AB Prions are proteins that adopt an alternative conformation, which becomes self-propagating. Some prions cause degeneration of the central nervous system (CNS). Once relegated to causing a group of rare disorders of the CNS such as Creutzfeldt-Jakob disease (CJD), prions also appear to play a role in more common illnesses such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). While CJD is caused by the accumulation of PrPSc prions, recent investigations demonstrate unequivocally that α-synuclein prions cause multiple system atrophy (MSA). Infectious MSA prions have been recovered from human brain samples stored in formalin for up to 20 years. Similar resistance to formalin was demonstrated for brain samples from sheep with scrapie. Increasing data argue that Aβ prions contribute to AD, α-synuclein prions to PD, and tau prions to some types of frontotemporal dementia (FTD). In this chapter, we confine our discussion to CJD, which typically presents with a rapidly progressive dementia as well as motor abnormalities. The illness is relentlessly progressive and generally causes death within 9 months of onset. Most CJD patients are between 50 and 75 years of age; however, patients as young as 17 and as old as 83 have been recorded. The role of prions in the pathogenesis of neurodegenerative diseases is reviewed in Chap. 417.