Mutations in LRRK2, located in the PARK8 locus, are the most common mutations in familial autosomal-dominant PD [22, 23], and LRRK2 polymorphisms are associated with increased PD risk in GWAS [24], suggesting a role of LRRK2 in both sporadic and familial PD. This evidence concerns the gene LRRK2 and Parkinson disease.