Several mutations in SNCA (encoding for α-syn) (reviewed in Nussbaum, 2018), APP and PSEN1/PSEN2 (encoding for the amyloid precursor protein (APP) and the presenilins that are involved in APP processing) (reviewed in Ayodele et al., 2021), MAPT (encoding for tau) (Ghetti et al., 2015) and TARDBP (encoding for TDP43) (Mackenzie and Rademakers, 2008) cause hereditary forms of PD/DLB, AD, FTD and ALS, respectively. This evidence concerns the gene APP and Parkinson disease.