Prion diseases are progressive neurodegenerative disorders that afflict humans and animals, with sporadic, inherited and acquired modalities; these pathological conditions are associated with an amyloidogenic misfolding of a normal glycoprotein, called cellular prion protein (PrPC), into a protease-insensitive isoform named prion protein Scrapie (PrPSc). The gene discussed is PRNP; the disease is prion disease.