PRNP and Alzheimer disease: Neurodegenerative disorders including Alzheimer’s disease (AD), the tauopathies, Parkinson’s disease (PD), multiple system atrophy (MSA), and PrP prion diseases such as Creutzfeldt–Jakob disease (CJD) are all progressive illnesses that cause increasing central nervous system (CNS) dysfunction and are eventually fatal (see [14]).