SNCA and Parkinson disease: The concentration of total α-synuclein was found to be significantly lower in PD patients (159.4 ± 61.6 ng/mL) compared to the control group (229.9 ± 64 ng/mL), while oligomeric α-synuclein and the ratio of oligomeric α-synuclein/total α-synuclein were increased in PD patients (respectively, PD: 47.8 ± 11.8 ng/mL vs. control: 39.2 ± 9.2 ng/mL and PD: 0.35 ± 0.18 vs. control: 0.19 ± 0.08).