Updating Our Definitions of Parkinson’s Disease for a Molecular Age

Clinical definitions of Parkinson’s disease (PD) are over 200 years old, while neuropathological definitions— which are still the basis of how we define the disease now— are over 100 years old. We argue that for both clinical care and therapeutic development, these definitions need updating for the molecular age in which we live. We highlight specific instances in which genetic or biochemical biomarkers are increasingly used for clinical trial enrollment in the neurodegenerative diseases, suggesting that molecular definition(s) of PD are already emerging. We review candidate biomarkers for PD-related pathologies and highlight the need for further validation.