SNCA and Parkinson disease: A small portion of PD cases is familial, which can be caused by highly penetrant mutations in Mendelian genes, both with autosomal dominant (SNCA, LRRK2, VPS35, EIF4G1, and CHCHD2) and with autosomal recessive (parkin, PINK1, DJ1, ATP13A2, FBXO7, PLA2G6, and DNAJC) modes of inheritance [5, 6].