This study aimed to (1) analyze oligomeric αSyn in the ankle and cervical skin biopsies of patients with PD, MSA, AP-Tau, and HC; (2) compare the diagnostic accuracy for PD of αSyn-PLA vs. P-αSyn and vs. 5G4 antibody according to the anatomical site; (3) evaluate pathologic αSyn and IENFD changes by skin biopsy longitudinally at 2 years follow-up in PD. The gene discussed is MAPT; the disease is multiple system atrophy.