Figure 1. Skin Biopsy Protocols.

Skin samples were taken from C7, thigh, and distal leg. We took in each skin site a second biopsy approximately 3 centimeters away from the first sample to increase the rate of phosphorylated α-synuclein (p-syn) positivity. The study protocol includes 2 pairs of skin samples taken from a single skin site (i.e., C7, thigh, or leg) 2–3 centimeters apart (red rectangle). In addition, in the remaining 2 skin sites, a pair of skin samples were taken for routine purpose (black rectangle). The skin site was chosen for the study considering the probability of finding p-syn in skin nerves, which is influenced by the specific clinical phenotype. Accordingly, the distal skin sites were mainly chosen in patients with autonomic or neuropathic disorders (protocols I and II), while in patients with parkinsonism and dementia, the proximal site was mainly used (protocol III). In 1 patient with Parkinson disease (PD) and 4 patients with progressive supranuclear palsy for the immunofluorescence reproducibility study and 2 patients with PD and 1 patient with Alzheimer disease for the comparative study 2 different skin sites were analyzed for the study protocol (10 samples/patient).