APOE and Parkinson disease: The clinical traits of PD, such as age at onset, cognitive progression, motor progression, composite progression, tremor dominant, and postural instability gait difficulty, have been found to be underpinned by additional biomarkers, including APOE, NTRK2, SLCO1B3, SLC28A3, AQP10, SNCAIP, ANO2, CADM1, PTPRD, GPR32, GPR321, SQOR, SULT1C2, GABRG2, CYP4Z1, CDH13, and FANCF. Significant evidence was found linking genetic variants linked to an increased risk of PD to reduced dopamine production, receptor recycling, oxidoreductase activity, and increased amyloid-beta accumulation.