PRNP and Myoclonus: In the sCJD subgroup alone, we found evidence (P < 0.001) that myoclonus (more prevalent in MM and VV genotypes), tremor (MV and VV genotypes), supranuclear ophthalmoparesis (MV genotype), and alien limb phenomenon (MM genotype) were modified by PRNP codon 129 genotype (Figs. S2 and S3).