Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of late-onset PD identified to date, with G2019S being the most frequent LRRK2 mutation, which is responsible for up to 1-2% of sporadic PD and up to 6% of familial PD cases. This evidence concerns the gene LRRK2 and Parkinson disease.