PRNP and sporadic Creutzfeldt-Jakob disease: Specific phenotypes and unusual symptoms could overlap in different PRNP mutations, or the same PRNP mutation could differ in phenotype: the D178N mutation could present as gCJD or FFI, determined by the type of codon 129 polymorphism; or the D178N–129M haplotype, expressing the FFI phenotype, corresponds to MM2-Thalamic (MM 2T or sporadic FI) in sporadic CJD (sCJD) [7].