Monoamine oxidase (MAO) is an enzyme of the mitochondrial outer membrane and catalyzes the oxidative deamination of biogenic amines throughout the body (1). MAO is critical in the neuronal metabolism of catecholamine and indolamine transmitters (2). Cultured skin fibroblasts show both MAO-A and MAO-B and both MAOs differ in molecular structure (1). MAO-A, the primary type in fibroblasts, preferentially degrades serotonin and norepinephrine (3). Only MAO-B is present in platelets and only