Wang Z, Becker K, Donadio V, et al. - In this retrospective and prospective diagnostic study involving skin samples from 160 autopsies and 41 biopsies, researchers developed sensitive and specific skin biomarkers for antemortem diagnosis of Parkinson disease (PD) and other synucleinopathies. They assessed autopsy and biopsy skin samples from neuropathologically and clinically diagnosed patients with PD and controls without PD. A statistically significant increase in pathological α-synuclein (αSyn^P) seeding activity was found in people with PD and synucleinopathies vs controls with tauopathies and nonneurodegenerative diseases. In patients with PD and non-PD synucleinopathies, skin αSyn^P has aggregation seeding activity and can be a biomarker for antemortem diagnosis of PD and other synucleinopathies.