A woman, aged 59 years, underwent a cortical biopsy that led to the diagnosis of Creutzfeldt-Jakob disease (CJD). A man, aged 46 years, underwent cranial surgery in the same department 3 days later for brain contusion, with an uneventful recovery. Twenty six months later, he developed clinical signs of CJD with a typical EEG pattern. Both cases exhibited features of the ataxic form of the disease with depletion of cerebellar granule cells, without kuru plaques or PrP deposits. PrP deposits were immunohistochemically observed in the cerebrum, spinal cord and peripheral nerve. Molecular genetic analysis performed on brain tissue revealed the codon 129 polymorphism to be Met129Met in the donor and Met129Val in the recipient. The shared cerebellar phenotype and the genotypic discrepancy between the two patients lead us to postulate that the cerebellar agent strain plays a major role in CJD phenotype and transmission.Une femme de 59 ans a subi une biopsie corticale, qui a mis en evidence la maladie de Creutzfeldt-Jakob (MCJ). Un homme de 46 ans a ete opere 3 j apres dans le meme service, a la suite d'un traumatisme cranien, dont il a gueri sans sequelles. Vingt-six mois plus tard, il developpa progressivement les signes cliniques et EEG d'une MCJ. Les deux cas se presentaient sous la forme ataxique , avec atrophie de la couche des grains du cervelet, mais sans plaques Kuru ni depots PrP dans le cervelet. Les depots PrP mis en evidence immunohistochimiquement touchent le cerveau, la moelle epiniere ainsi que le nerf peripherique. L'analyse moleculaire n'a pas montre de mutation sur le gene PRNP, mais des alleles differents au codon polymorphe 129, ou le donneur etait Met129Met et le receveur Met129Val. La similitude phenotypique alors que le genotype est different plaide en faveur du role primordial, dans ces conditions, de la souche de l'agent dans le determinisme du phenotype et de la transmission.