LRRK2 and Parkinson disease: The most prevalent LRRK2 amino acid substitution, G2019S, is responsible for ~40% of familial and sporadic PD in Arab samples from North Africa, ~30% of familial PD in Ashkenazi Jewish populations, up to 6% of familial cases in Europe and up to 3% of apparently sporadic PD in Europe and North America [2,23].