Different PRNP mutations are associated with distinct clinical and neuropathological phenotypes: genetic Creutzfeldt-Jakob disease (gCJD), fatal familial insomnia (FFI), Gerstmann-Sträussler-Scheinker (GSS) syndrome, PrP cerebral amyloid angiopathy (PrP-CAA) and PrP systemic amyloidosis.1,2. Here, PRNP is linked to fatal familial insomnia.