We recently characterized tau protein in skin and showed that its concentration and amount of 4R tau isoform transcript level is higher in skin biopsy of tauopathies than healthy controls (HC) and synucleionopathies22; therefore, we hypothesized that we could exploit tau-SAA in skin samples of PSP and CBD and determine its diagnostic capacity vs PD and MSA. This evidence concerns the gene MAPT and multiple system atrophy.