Pursuant to Western countries (Table 1), in 1999, Parchi et al. found that for 300 sporadic CJD patients, studied between 1968 and 1998 from North America (United States and Canada) and Europe (France, Italy, United Kingdom, Finland, and Denmark), the shortest average duration of symptoms was 3.9 months (range 1–18) for (203) patients homozygous for methionine/methionine (MM) at codon 129 in the PRNP, and the longest duration was 17.1 months (range 5–72) for (27) patients with the methionine/valine (MV) polymorphism [12]. The gene discussed is PRNP; the disease is Creutzfeldt Jacob disease.