SNCA and Parkinson disease: The plasma levels of total α-synuclein and ratio of pS129-α-synuclein/total α-synuclein were also increased in PD patients compared to controls (total α-synuclein: PD vs. controls: 1302.3 ± 886.6 fg/mL vs. 76.4 ± 33.5 fg/mL, p < 0.001; pS129-α-synuclein/total α-synuclein ratio: PD vs. controls: 2.8 ± 1.1% vs.1.1 ± 0.6%, p = 0.01, Table 2, Figure 1B,C).