Publisher Summary Dopamine beta-hydroxylase (DBH) deficiency, also known as norepinephrine deficiency, is a rare congenital disorder caused by the absence of the enzyme, DBH, which converts dopamine to norepinephrine. The disorder is characterized by a lack of sympathetic noradrenergic function, and affected individuals exhibit substantial deficits in autonomic regulation of cardiovascular function. In patients with DBH deficiency, the perinatal period has been complicated by vomiting, dehydration, hypotension, hypothermia, and profound hypoglycemia requiring repeated hospitalization. Despite the lack of norepinephrine, persons with DBH deficiency apparently have relatively normal mental status. Results from five patients revealed no substantial deficits in performance on a battery of cognitive tasks that have been proposed to depend on normal noradrenergic function. Patients with DBH deficiency are unique in that they have virtually no norepinephrine or epinephrine or their metabolites. Without norepinephrine-mediated negative feedback on tyrosine hydroxylase, cytosolic dopamine production is amplified. Although catecholamines must be assayed to verify the diagnosis of DBH deficiency, a number of physiological and pharmacological tests can be used to assess autonomic function in these patients.