PRNP and Creutzfeldt Jacob disease: CJD is associated with the formation of the pathological prion protein (PrPCJD) mostly in brain tissue and therefore classified in six major clinicopathological subtypes based on the genotype at the methionine (M)/valine (V) polymorphic codon 129 of the PRNP gene and the type (1 or 2) of PrPCJD.