This classification, known as SynNeurGe, categorizes PD based on three main etiological factors: (1) PD associated with pathological aggregation of α-synuclein, as seen in multiple system atrophy; (2) PD with evidence of underlying neurodegeneration, identified through neuroimaging procedures; and (3) PD with documented pathogenic gene variants. The gene discussed is SNCA; the disease is Parkinson disease.