Familial PD is usually caused by mutations in PD-related genes, including SNCA (Puschmann, 2013), Parkin (Gao and Hong, 2011; Puschmann, 2013), PINK1 (Crosiers et al., 2011), DJ-1 (Blauwendraat et al., 2020), LRRK2 (van der Vegt et al., 2009), ATP13A2 (Crosiers et al., 2011), and so on. The gene discussed is LRRK2; the disease is Parkinson disease.