Dopamine Beta-Hydroxylase Deficiency

Clinical characteristics Dopamine beta-hydroxylase (DBH) deficiency is characterized by lack of sympathetic noradrenergic function but normal parasympathetic and sympathetic cholinergic function. Affected individuals exhibit profound deficits in autonomic regulation of cardiovascular function that predispose to orthostatic hypotension. Although DBH deficiency appears to be present from birth, the diagnosis is not generally recognized until late childhood. The combination of ptosis of the eyelids in infants and children, together with hypotension, is suggestive of the disease. In the perinatal period, DBH deficiency has been complicated by vomiting, dehydration, hypotension, hypothermia, and hypoglycemia requiring repeated hospitalization; children have reduced exercise capacity. By early adulthood, individuals have profound orthostatic hypotension, greatly reduced exercise tolerance, ptosis of the eyelids, and nasal stuffiness. Presyncopal symptoms include dizziness, blurred vision, dyspnea, nuchal discomfort, and chest pain; symptoms may worsen in hot environments or after heavy meals or alcohol ingestion. Life expectancy is unknown, but some affected individuals have lived beyond age 60 years. Diagnosis/testing The diagnosis of DBH is established in a proband with profound neurogenic orthostatic hypotension, minimal or absent plasma concentrations of norepinephrine and epinephrine, and a five- to tenfold elevation of plasma dopamine; it is confirmed with identification of biallelic pathogenic variants in DBH by molecular genetic testing. Management Treatment of manifestations: Administration of L-threo-3,4-dihydroxyphenylserine (droxidopa) restores norepinephrine and alleviates the orthostatic hypotension and other symptoms. Affected individuals do not respond as well to standard therapeutic approaches for autonomic failure. Surgery can correct ptosis. Surveillance: Renal function (measurement of plasma creatinine and BUN concentrations) is assessed every two years or more often if loss of renal function is evident; plasma magnesium and potassium should also be assessed. Yearly evaluation of efficacy of droxidopa against orthostatic hypotension as dosage adjustment may be required. Consultation with autonomic specialist prior to surgery or becoming pregnant. Agents/circumstances to avoid: Untreated individuals should avoid hot environments, strenuous exercise, standing motionless, and dehydration. Pregnancy management: Routine blood pressure monitoring during pregnancy and delivery, with adjustment of droxidopa dosage as needed; extra doses of droxidopa may be required during delivery and dose adjustment may be required post partum. Genetic counseling DBH deficiency is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives is possible if both pathogenic variants in the family are known. Once the DBH pathogenic variants have been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic testing are possible.