Dopamine - b - Hydroxalase Deficiency is characterized by sympathetic noradrenergic denervation and adrenomedullary failure, but intact vagal and sympathetic cholinergic function. It is a rare, congenital, nonhereditary form of severe orthostatic hypotension, caused by complete absence of Dopamine-b - Hydroxylase, the enzyme involved in the conversion of dopamine to norepinephrine.

Clinical Presentation: The presence of orthostatic hypotension has not been documented prior to the age of 20, in those who are afflicted with Db H deficiency. However, during childhood impaired exercise tolerance, fatigue, and episodes of fainting and syncope, are frequently present. Symptoms from orthostatic intolerance become worse in late adolescence and in early adulthood. Patients will experience more intense symptoms due to orthostatic intolerance in the morning hours, heat, and after alcohol consumption, however, they do not experience symptoms after eating. Upon physical examination, patients may reveal a low normal (supine) blood pressure and a low (supine) heart rate. In the upright position, systolic blood pressure always falls below 80 mm Hg, However, opposite of other forms of autonomic failure, the compensatory rise in heart rate is completely preserved. Sweating is normal, and the pupils may be somewhat small, but respond to light and accommodations.

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Last modified: Monday January 28, 2008.