Given these limitations, there is an ongoing shift toward biomarker-based PD diagnostics—a way forward seems to be paved by the two sets of recently published biological criteria: SynNeurGe (Synuclein-Neurodegeneration-Genetics) research diagnostic criteria for biological classification of PD (37) and NSD-ISS (Neuronal Synuclein Disease Integrated Staging System) (38). The gene discussed is SNCA; the disease is Parkinson disease.