PRNP and prion disease: Prions are protein-only infectious agents that form due to conformational change in the cellular prion protein (PrPC) from its native state to the more stable scrapie form (PrPSc) and cause “prion diseases,” rare but fatal neurodegenerative disorders that include scrapie in sheep, chronic wasting disease in deer, bovine spongiform encephalopathy in cows, and Creutzfeldt-Jakob disease in humans (Prusiner, 2013).