Prion diseases are slowly progressive, usually fatal brain diseases characterized by the development of vacuoles in the gray matter, prominent gliosis involving astroglia and microglia, and deposition in brain of aggregated partially protease-resistant isoforms (PrPSc or PrPres) derived from host-encoded normal prion protein (PrPC or PrPsen) [6]. This evidence concerns the gene PRNP and prion disease.