Multiple lysosomal / endosomal genes have been linked to PD (Nalls et al., 2019; Ebanks et al., 2020) and it is likely that even in absence of known pathogenic mutations in the cohorts included in the present study, polygenic risk factors (see Iwaki et al., 2020) and/or environmental factors act synergistically with the mutant LRRK2 to drive pathogenesis. This evidence concerns the gene LRRK2 and Parkinson disease.