PRNP and fatal familial insomnia: The missense mutation NM_000311.5:c.532G>A (p.Asp178Asn) in the prion protein gene (PRNP) results in two different phenotypes, either familial Creutzfeldt‐Jacob disease (fCJD; OMIM# 123400) or fatal familial insomnia (FFI; OMIM# 600072), depending on whether the PRNP cis codon 129 is methionine or valine, with the former typically associated with FFI and the latter with fCJD.65