PRNP and multiple system atrophy: Associations of MSA with the genes COQ2, SNCA, MAPT, and PRNP have been discussed.15–20 One prior genome-wide association study (GWAS) did not identify hits of statistical significance at a genome-wide level, despite the analysis of 918 cases and 3864 controls.21 This GWAS had mainly included clinically diagnosed MSA cases.