Though the etiology circumscribing the selective loss of SNc DAergic neurons in PD is not fully understood, we do know that reportedly ~5–10% of PD patients display mutations in genes such as DJ-1, PTEN-induced kinase 1 (PINK-I), leucine-rich repeat kinase 2 (LRRK2) G2019S, park-1/Synuclein (SNCA), ubiquitin-carboxy-terminal-hydrolase L1, parkin (Del3-5, T240R, Q311X) [15–18], ATP13A2 (Park 9), β-glucocerebrosidase and mitochondrial proteins such as park 13 Omi/Htra2, Complex I [19–22]. The gene discussed is LRRK2; the disease is Parkinson disease.