PRNP and fatal familial insomnia: Familial prion diseases, including Creutzfeldt-Jakob disease (CJD), fatal familial insomnia (FFI), and Gerstmann-Sträussler-Scheinker syndrome (GSS), are all linked to mutations in the gene encoding PrPC, PRNP, where at least 20 different mutations which trigger PrP misfolding and the generation of different levels and conformers of PrPRES[2].