Natural prion disorders include scrapie in sheep and goats, bovine spongiform encephalopathy (BSE) in cattle, transmissible mink encephalopathy (TME) in mink, chronic wasting disease (CWD) in cervids, and Kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker syndrome (GSS), fatal familial insomnia (FFI) and variably protease-sensitive prionopathy (VPSPr) in humans, which arise either sporadically–putatively spontaneous misfolding of PrPC–or are caused by mutations in the PrP encoding gene that are inherited as an autosomal dominant trait [4, 5]. Here, PRNP is linked to fatal familial insomnia.