Furthermore, polymorphisms in the genes encoding for monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B), which metabolize dopamine, could represent probable risk factors for PD [21], as well as polymorphisms in the dopamine D2 receptor (DRD2) gene that could predispose to PD [22]. The gene discussed is MAOB; the disease is Parkinson disease.