Vivacqua et al. quantified the levels of oligomeric α-synuclein and total α-synuclein, as well as the total α-synuclein/oligomeric α-synuclein ratio in the saliva samples of 100 PD patients, 80 HC subjects, and 20 patients with progressive supranuclear palsy (PSP). This evidence concerns the gene SNCA and Classical progressive supranuclear palsy.