Limitations of this study include the absence of few rare mutations (e.g., G114V, E200G, and V189I) that have been linked to a CJD phenotype, and the small/imbalanced sample sizes of patient subgroups that are virtually inevitable, given the highly heterogeneous prevalence of the PRNP variants and phenotypes, which is also limiting the power of the statistical comparison within each of the gCJD groups, especially for demographic data and clinical features. This evidence concerns the gene PRNP and Creutzfeldt Jacob disease.