Genetic forms of prion diseases are associated with mutations in the human prion protein gene (PRNP) and comprise familial CJD (fCJD), Gerstmann–Straussler–Scheinker (GSS) syndrome [4], fatal familial insomnia (FFI) [5] and prion protein cerebral amyloid angiopathy [6]. This evidence concerns the gene PRNP and prion disease.