Human familial forms of the disease are linked to specific mutations in the PrP gene, PRNP, and include Gerstmann-Strussler-Scheinker syndrome (GSS), familial Creutzfeldt-Jakob disease (fCJD), and fatal familial insomnia.
FFI is associated with an aspartic acid to asparagine mutation at codon 178 of the PrP gene (D178N) in conjunction with methionine at the codon 129 polymorphic site on the mutant allele (cis-129M).