PRNP and Creutzfeldt Jacob disease: Although individual mutations cause some additional, unique features that can distinguish their associated phenotypes from others assigned to the same disease type and, furthermore, the different disease types have some overlap (for example, CJD and GSS can both affect the cortex and cerebellum, but to a different extent), mutations in PRNP cause diseases that are consistently assigned to one of these three disease types (Kovács et al., 2002).