SNCA and Parkinson disease: To this aim, we combined the specific RT-QuIC expertise of two laboratories, one in Italy (ITA-lab) and one in the USA (USA-lab), to set up a precise α-synuclein RT-QuIC (αSyn_RT-QuIC) protocol for the analysis of OM samples collected from well-characterized patients with MSA-P, MSA-C, PD, and healthy subjects (HS).