Similar genetic susceptibility in iatrogenic and sporadic Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease (CJD) is one of the transmissible spongiform encephalopathies (TSEs). In all TSEs host susceptibility is an important factor in the development of clinical disease. The prion protein (PrP) gene appears to confer the main component of this susceptibility. The appearance of spontaneous neurodegeneration in PrP transgenic mice carrying a human mutation has raised the possibility that the origin of sporadic CJD is solely genetic. We studied PrP codon 129 polymorphism in 23 of the 25 CJD cases in France related to human growth hormone (hGH) therapy. They constitute the largest and most homogeneous hGH-related iatrogenic CJD population yet analysed. All these CJD cases were homozygous at codon 129, compared with only 50% in the healthy control group (P < 0.00002). These iatrogenic cases also displayed a genotype frequency distribution similar to that observed in sporadic CJD. These results underline the importance of the PrP gene and especially the homozygous codon 129 genotype in determining the risk of developing CJD after contamination by a TSE agent. They also suggest that highly susceptible individuals may exist and raise the possibility that sporadic CJD may have an environmental origin.