PRNP and Creutzfeldt Jacob disease: As the most significant example of the coexistence of GSS and CJD features, GSS patients carrying the PRNP P102L-129M haplotype may manifest either a rapidly progressive CJD-like phenotype with both spongiform changes and amyloid plaques or a slowly progressive “pure” GSS phenotype with amyloid plaques, but no spongiform changes.