PRNP and early-onset autosomal dominant Alzheimer disease: Disease-specific misfolded protein/s found in the brain include, for example, amyloid-beta (Aβ) and hyperphosphorylated Tau protein in Alzheimer’s disease (AD), α-synuclein in Parkinson’s disease (PD), multiple system atrophy (MSA), the prion protein (PrP) in prion diseases, and SOD1 in Lou Gehrig’s disease.