Prion disease can only happen if the brain produces PrP, the protein that misfolds to cause the disease. Drugs are being developed to lower the amount of PrP in the brain which will prevent or stop the disease. To establish the efficacy of those drugs, it is necessary to measure PrP in spinal fluid in order to figure out whether it was reduced. The investigators have been collecting spinal fluid from people at risk for genetic prion disease to answer this question, and the new grant from CJD Foundation will enable the team to extend the timeline of the study and look at long-term stability in PrP measurements in spinal fluid over more than one year.