PRNP and Creutzfeldt Jacob disease: The mutation at codon 200 of PRNP, which results in a glutamic acid substitution by lysine (E200K) in PrP, is one of the most prevalent, being responsible for the high incidence of CJD amongst Libyan Jews and in areas of Slovakia and Chile, and is recognized in many other countries (Goldfarb et al., 1990, 1991; Hsiao et al., 1991; Brown et al., 1992; Collinge et al., 1993; Kovacs et al., 2002).