(A) individual data for control subjects (CTRL) and patients with idiopathic Parkinson disease (iPD) or mutations in SNCA, PRKN, LRRK2, GBA, or digenic LRRK2/GBA. Dashed line shows the upper limit of CTRLs. Horizontal lines indicate median values in each group. Abbreviations: ns=not significant. (*) p < 0.05, (**) p < 0.01, (***) p < 0.001, and (****) p < 0.0001 vs. CTRL. (B) Representative confocal microscopic images of immunoreactive α-syn (green), tyrosine hydroxylase (TH, red), smooth muscle actin (blue), and α-syn colocalized with TH (yellow) in arrector pili muscles from skin biopsies. Scale bars = 50 μm for main image, 20 μm inserts. Note that the iPD, SNCA, LRRK2, and GBA groups have elevated colocalization indices compared to CTRL.