In 1997, the first PD-associated mutation was discovered in the SNCA gene [13], originating a highly productive period of gene hunting that resulted in the identification of several PD-related genes, with either autosomal dominant (e.g., SNCA, LRRK2, VPS35) or autosomal recessive (e.g., PRKN, PINK1, DJ1) modes of inheritance [14]. The gene discussed is LRRK2; the disease is Parkinson disease.