Pathogenic mutations in autosomal dominant genes [leucine-rich repeat kinase 2 (LRRK2), α-synuclein (SNCA) and vacuolar protein sorting 35, yeast, homolog of (VPS35)] as well as biallelic mutations in autosomal recessive (AR) genes [PRKN, Parkinsonism associated deglycase (PARK7) or DJ-1, PTEN-induced putative kinase 1 (PINK1) and F-box protein 7 (FBXO7)] cause Mendelian PD (2). The gene discussed is SNCA; the disease is Parkinson disease.