DBH and Menkes disease: In the brain of patients with MD, the deficiency of Cu adversely affects the physiological function of Cu-dependent enzymes such as dopamine-β-hydroxylase (DβH), which is essential for synthesizing the neurotransmitter.54 Infants with MD present with high levels of dihydroxyphenylalanine, the precursor of catecholamines, suggesting reduced DβH activity.54,55 The impaired function of DβH may lead to impaired synaptogenesis and axonal growth, manifesting as hypotonia and seizures.