These proteins include Aβ (amyloid-β peptide) and Tau, both being associated with Alzheimer’s disease (AD), α-synuclein (α-Syn)—Lewy body disease (LBD) and Parkinson’s disease (PD), huntingtin protein (Htt)—Huntington disease (HD), islet amyloid polypeptide (IAPP)—diabetes type II, and prion protein (PrP)—Creutzfeldt–Jakob disease (CJD) (reviewed in [4]). Here, PRNP is linked to juvenile Huntington disease.