PRNP and fatal familial insomnia: Inherited cases constitute approximately 10–15% of human PrDs and are closely associated with dozens of mutations in the PRNP gene, including genetic CJD (gCJD), fatal familial insomnia (FFI), and Gerstmann-Sträussler-Scheinker (GSS) syndrome (Shi et al., 2015b,2021).