A significant difference was found in the LBD and MSA synucleinopathy patient groups of the present study, where it was decreased, which could suggest that synucleinopathy patients have a larger BBB and/or Tf transport disruption, or higher consumption/occupation of the protein, than 4RT tauopathy patients (Zeman et al. 2000; Song et al. 2011; Ayton et al. 2016; Al-Bachari et al. 2020). Here, TF is linked to synucleinopathy.