PSEN1 and Parkinson disease: Rare functional variants in APP (Schulte et al., 2015) and pathogenic mutations in PSEN1, and PSEN2 have been also reported in PD patients (Takao et al., 2002; Jimenez-Escrig et al., 2004; Puschmann et al., 2009; Niwa et al., 2013).