Dopamine Beta-Hydroxylase Deficiency
What else is it called?
- Dopamine β-hydroxylase
- Noradrenaline deficiency
- Norepinephrine deficiency
- DBH deficiency
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What causes it?
This disorder is caused by a problem in the DBH gene. This gene provides instructions for providing dopamine β-hydroxylase enzyme which converts dopamine to norepinephrine. Norepinephrine works like a chemical transporter that transmits signals between nerve cells.
If you have a problem in the DBH gene, you will not produce functional dopamine β-hydroxylase enzyme. Therefore, you will not be able to convert dopamine to norepinephrine and your body will not have enough of it. This will cause you difficulties with regulating blood pressure and other autonomic nervous system problems.
How common is it?
We do not know how many people have this disorder. It is very rare with only a small amount of cases that are known. Due to its rarity, it is also unknown whether it affects more males or females. All affected individuals so far have been of western European descent.
What are the signs and symptoms?
The onset of the signs and symptoms is in early infancy right after birth. However, the deficiency does not have to be necessarily diagnosed before childhood. Some symptoms appear throughout life.
Signs and symptoms in infancy may include:
- Episodes of vomiting
- Decreased blood pressure (Hypotension)
- Difficulty maintaining body temperature
- Low blood sugar (Hypoglycemia)
- Delay in opening of the eyes has occurred
- Droopy eyelids (Ptosis)
In childhood, you may develop:
- Markedly reduced exercise capacity
Symptoms usually get worse in adolescence and may include:
- Profoundly decreased blood pressure (Hypotension)
- Greatly reduced exercise tolerance
- Droopy eyelids (Ptosis)
- Nasal stuffiness
- Insulin resistance – found in women
- Retrograde or prolonged ejaculation in men
Other signs and symptoms may include:
- Sleep disturbances
- Reduced tendon reflexes
- Abnormally increased production of urine during the night (Nocturia)
- Difficult or labored breathing (Dyspnea)
- Chest pain
- A reduction in erythrocytes volume or hemoglobin concentration (Anemia)
- High palate
- Abnormally low muscle tone (Hypotonia)
As a person gets older, they may experience episodes of a sharp drop in blood pressure that causes dizziness, blurred vision, or fainting. These episodes are getting more severe when getting out of bed in the morning, during hot weather, and after heavy meals or alcohol. Problems with blood pressure also cause extreme fatigue during exercise.
The prognosis varies greatly from case to case. Some individuals have survived past 60 years of life.
How is it diagnosed?
You will be diagnosed after a clinical examination by your specialist or doctor. However, as the signs and symptoms of this disorder are similar to other conditions, you will need further tests. Doctors will analyse your blood using a special test. The diagnosis is confirmed by DNA test.
Can it be treated?
Unfortunately, there is no treatment for this deficiency. Therefore, treatment is focused on managing individual symptoms and providing comfort and relief in the form of supporting the individual and any family members. A multi-disciplinary team of specialists and support networks will be involved in the management of the condition and to offer practical and emotional support.
The most effective supportive treatment has been proven administration of L-threo-3,4-dihydroxyphenylserine (Droxidopa). The administration of Fludrocortisone and Midodrine may also be of benefit. Surgery can correct ptosis.
Do my family need to be tested?
Dopamine beta-hydroxylase deficiency can only be passed on to a child if both parents have a copy of the faulty gene. This is called autosomal recessive inheritance. A person who has a copy of the faulty gene is known as a carrier.
If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have.
If the child only inherits one copy of the faulty gene, they will be a carrier but will not have the disorder. In some rare cases, carriers have had mild symptoms of the disorder for which they carry the faulty gene.
Once you are diagnosed, you can speak to a genetic counsellor. They can explain how you may have inherited Dopamine beta-hydroxylase deficiency. They can also tell you about genetic testing for the rest of your family. They can provide advice and support if you go on to have children of your own.
References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing email@example.com [Resource Library No: AAP002].