A Natural History Study of Preclinical Genetic Creutzfeldt-Jakob Disease (CJD)

Inclusion Criteria: * First--degree relative of an E200K gCJD patient. * Age 50 years or older at baseline. * Willingness to undergo genetic testing. * Ability to provide written informed consent under GCP, ICH, and local regulations. * Willingness and ability to comply with scheduled visits, required study procedures, and laboratory tests. Exclusion Criteria: * a clinical diagnosis of CJD * Any other medical or psychiatric condition or laboratory abnormality, which in the opinion of the investigator might preclude participation. * Previously obtained MRI scan with evidence of clinically significant neurological disorder other than CJD. * Current anticoagulant treatment (e.g Non-vitamin K Antagonist Oral Anticoagulants (NOACs), Warfarin, Low Molecular weight Heparin) that might preclude safe completion of LP. * Conditions that preclude the safe performance of LP, such as severe lumbar spinal disease, bleeding diathesis, or clinically significant coagulopathy or thrombocytopenia. * Conditions that preclude the safe performance of MRI scannings such as subjects who have a pacemaker, aneurysm clips, artificial heart valves, ear implants, metal fragments or foreign objects in the eyes, skin, or body, or any other known contra-indication for MRI. * Active malignant disease.