The phenotypic expression of different mutations in transmissible familial Creutzfeldt-Jakob disease.

Cases of familial Creutzfeldt-Jakob disease (CJD) with mutations in the PRNP gene were analyzed for distinctive clinico-pathological and experimental transmission characteristics. An insert mutation within the region of codons 51 to 91 was associated with a markedly early age at onset and prolonged course of illness. Point mutations at codons 178 and 200 were also associated with ages at onset, durations of illness, and clinical symptom profiles that differed from sporadic CJD. The age at onset of illness in each group was correlated with the length of incubation periods in primates inoculated with their brain tissue, suggesting that the early onset of familial CJD results not from a time shift of the initiating event, but from an accelerated pre-clinical (incubation) phase of disease, perhaps due to a more rapid formation of amyloid induced by a mutationally-altered precursor protein template.