COMT and Parkinson disease: Meanwhile, eight PD risk factor genes—namely, glucocerebrosidase (GBA), mitochondrial transcription factor A (TFAM), Nuclear factor erythroid 2-related factor 2 (NFE2L2), macrophage metalloelastase (MMP12), major histocompatibility complex, class II, DR α (HLA-DRA), Catechol-O-methyltransferase (COMT), monoamine oxidase B (MAOB) and dopamine β-hydroxylase (DBH)—were detected [12].