MAOB and Parkinson disease: The risk of both PD and SCZ is higher in patients with the Val158Met polymorphism in the gene for catechol-O-methyltranferase (COMT)[1,2], the rs1799836 polymorphism in the gene for monoamine oxidase B (MAOB) [1,3], or the C(-1562)T polymorphism in the gene encoding matrix metalloprotease-9 (MPP-9) [4,5].