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Chapter 24 : Prion Diseases
Category: Clinical Microbiology
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Transmissible spongiform encephalopathies (TSEs), or prion diseases, are unlike any other malady. Prion diseases have long, largely asymptomatic incubation periods. Although the name would suggest all TSEs are acquired, in fact most prion diseases have no apparent cause and are called sporadic. TSEs are caused by a novel contagion once referred to as a slow virus and now called a prion. Scrapie is the oldest known TSE; it was first described in Europe at least 250 years ago. The presence of amyloid in the brains of kuru victims suggested a relationship with a much broader category of diseases. The relative resistance of a prion to proteinase K (PK) digestion is strain dependent. Worldwide, familial prion diseases account for 10 to 15% of all prion diseases. Kuru was eliminated when local authorities intervened to persuade members of the Fore tribe to stop ritual cannibalism. Diagnosing a prion disease is, by necessity, a diagnosis by elimination, since they are extremely rare. TSEs comprise a set of rare fatal neurological diseases found in many mammals and include such human diseases as Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker (GSS), fatal familial insomnia (FFI), and kuru.
Version of mouse PrPC (note that the sugar antennae are represented in their most complex form) ( 145 ).
Catalog of polymorphisms found in human PrPC. Amino acid codes: A, alanine; D, aspartic acid; E, glutamic acid; F, phenylalanine; G, glycine; H, histidine; I, isoleucone), K, lysine; L, leucine; M, methionine; N, asparagine; P, proline; Q, glutamine; R, arginine; S, serine; T, threonine; V, valine; Y, tyrosine ( 114 , 145 ).
WHO case definition for CJD ( 182 )
WHO case definition for vCJD ( 183 )