Like many NDs, PD is a mostly sporadic disease; however, genes have been identified to be causative when mutated, including SNCA, VPS35, and LRRK2, resulting in autosomal dominant forms of PD, and Parkin and PINK1 to be the most common genes mutated in autosomal recessive forms of PD [3,65]. The gene discussed is LRRK2; the disease is Parkinson disease.