SYNJ1 and Parkinson disease: Among genetic PD, PARK20 is a rare autosomal recessive juvenile Parkinson’s form due to mutations in Synaptojanin1 (Synj1), a phosphatidylinositol phosphatase (PtdInsPP) (Krebs et al., 2013; Quadri et al., 2013; Olgiati et al., 2014).