PRNP and Creutzfeldt Jacob disease: Most significantly, a further PrPSc fragment with an electrophoretic mobility of approximately 20 kDa, intermediate between types 1 and 2, and designated as PrPSc “i”, characterizes the sporadic and iatrogenic CJD cases showing amyloid plaques of the kuru type and carrying at least one M allele at PRNP codon 129 [18,31,32,34,35] (Figure 1).