LRRK2 and Parkinson disease: There are six genes unequivocally linked to heritable, monogenic PD, which includes mutations in SNCA (PARK1 = 4) and LRRK2 (PARK8) that are responsible for autosomal dominant PD forms, while mutations in Parkin (PARK2), PINK1 (PARK6), DJ-1 (PARK7), and ATP13A2 (PARK9) are accountable for PD with an autosomal recessive (AR) mode of inheritance (Thomas and Beal, 2007; Kalia and Lang, 2015; Day and Mullin, 2021).