Declaration of interests GUH reports participation in industry-sponsored research projects from AbbVie, Bial, Biogen, Biohaven, Novartis, Sanofi, Takeda, and UCB; served as a consultant for AbbVie, Alzprotect, Aprineua, Asceneuron, Bial, Biogen, Biohaven, Kyowa Kirin, Lundbeck, Novartis, Retrotope, Roche, Sanofi, and UCB; received honoraria for scientific presentations from AbbVie, Bayer Vital, Bial, Biogen, Bristol Myers Squibb, Kyowa Kirin, Roche, Teva, UCB, and Zambon; received publication royalties from Academic Press, Kohlhammer, and Thieme; and holds a patent on the Treatment of Synucleinopathies (US patent: US 10,918,628 B2; European patent: EP 17 787 904·6–1109/3 525 788). CHA reports consultant fees from Cionic, CND Life Science, Jazz, Neurocrine, Precon Health, and XW Pharma. DB reports having served on advisory boards of UCB Pharma and ACImmune; received honoraria from Biogen, UCB Pharma, and Novartis; and her research was supported by UCB Pharma, the European Union, Novartis Pharma, and Lundbeck. CK is deputy editor of Movement Disorders and associate editor of Annals of Neurology; serves as a medical adviser to Centogene for genetic testing reports in the fields of movement disorders and dementia, excluding Parkinson's disease; serves as a medical advisor to Retromer Therapeutics; received honoraria for scientific presentations from Bial and Desitin; and does not hold any stocks or stock options with any companies that are connected to Parkinson's disease or to any of the topics in this Personal View; WP reports personal fees from AbbVie, AFFiRiS, AstraZeneca, Bial, Boston Scientific, Britannia, Intec, Ipsen, Lundbeck, NeuroDerm, Neurocrine, Denali Pharmaceuticals, Novartis, Orion Pharma, Prexton, Teva, UCB, and Zambon; royalties from Thieme, Wiley Blackwell, Oxford University Press, and Cambridge University Press. RP received personal fees as an advisor from Takeda, Roche, Biogen, AbbVie, Curasen, Lilly, Novartis, Eisai, Merck, and Vaxxinity; and received a stipend from the International Parkinson and Movement Disorder Society. AJS chairs a data safety monitoring board for Neurocrine; serves on a data safety monitoring board for AskBio; serves as an advisor to Capsidia; receives a stipend from the International Parkinson & Movement Disorder Society as editor-in-chief of Movement Disorders. AEL has served as an advisor for AbbVie, AFFiRis, Alector, Amylyx, Aprinoia, Biogen, BioAdvance, BlueRock, Biovie, Bristol MyersSquibb, CoA Therapeutics, Denali, Janssen, Jazz, Lilly, Novartis, Paladin, Pharma 2B, PsychoGenetics, Retrophin, Roche, Sun Pharma, and UCB; received honoraria from Sun Pharma, AbbVie and Sunovion; is serving as an expert witness in litigation related to paraquat and Parkinson's disease; received publishing royalties from Elsevier, Saunders, Wiley-Blackwell, Johns Hopkins Press, and Cambridge University Press; and co-shares a patent for diagnostic assays for movement disorders that includes alpha-synuclein seeding assay testing. TFO reports no competing interests.