It has been shown that mutations in genes, such as leucine-rich repeat kinase 2 (LRRK2), α-synuclein, PTEN-induced kinase 1 (PINK1), and parkin, are linked to familial PD cases, but these account for only 10–15% of total PD cases (Table 1) [3]. The gene discussed is LRRK2; the disease is Parkinson disease.