LRRK2 and Parkinson disease: The LRRK2 6099G > A (Gly2019Ser) mutation leads to the most frequent substitution in Caucasians, which typically explains 0.5–2.0% of cases of SPD and 5% of familial Parkinsonism (Kachergus et al. 2005; Gilks et al. 2005; Di Fonzo et al. 2005).