5–10% of PD patients have a heterozygous mutation in the gene GBA, encoding the lysosomal protein glucocerebrosidase (Beavan and Schapira 2013), and up to 6% of sporadic PD patients have a mutation in LRRK2, encoding leucine-rich repeat kinase 2 (Bardien et al. 2011). This evidence concerns the gene LRRK2 and Parkinson disease.