LRRK2 and Parkinson disease: In addition to causal mutations in the LRRK2 coding sequence, association studies and genome-wide association studies have revealed that other genetic variations at the LRRK2 locus modulate risk for sporadic PD (Satake et al., 2009; Simón-Sánchez et al., 2009; Ross et al., 2011; Nalls et al., 2019).