LRRK2 and Parkinson disease: The LRRK2 G2019S mutation alone explains up to 6% familial and 3% sporadic PD cases in Europeans (Di Fonzo et al, 2005; Gilks et al, 2005) and up to 20% of total cases among Ashkenazy Jews (Ozelius et al, 2006) or 40% in North African Berbers (Lesage et al, 2006).