Subtypes of Parkinson's Disease: What Do They Tell Us About Disease Progression?

Parkinson's disease is a widely heterogeneous disorder with a broad list of motor and nonmotor manifestations. Identifying subtypes of Parkinson's disease is one of the top clinical and research priorities. This review aims to summarize the most valid conventional and recent subtyping solutions that have been introduced so far and to update our current knowledge with recent discoveries on the association between subtypes and disease progression. We also discuss the challenges of subtyping in the context of Parkinson's disease, stability of the subtypes over time, and potential clinical implications. Sophisticated evidence show that there are distinct subtypes of Parkinson's disease with diverging trends of progression. A more holistic view of subtyping to merge traditional motor features with key nonmotor manifestations is a promising approach to identify subgroups with different prognosis. Subtyping could improve further by adding continuing to add data from imaging, CSF, and genetic biomarkers.