These include α-synuclein (α-Syn) in Parkinson’s disease (PD) [8,9,10], amyloid beta (Aβ) and Tau in Alzheimer’s disease (AD) [11,12,13], prion protein (PrP) in prion disease [14], and islet amyloid peptide (IAPP), also known as amylin, in type 2 diabetes mellitus (T2DM) [15,16,17,18,19]. The gene discussed is IAPP; the disease is early-onset autosomal dominant Alzheimer disease.