Aromatic l-amino acid decarboxylase (AADC) deficiency is a rare disorder that decreases the activity of aromatic l-amino acid decarboxylase, affecting the ways signals are passed between cells in the nervous system.
The symptoms of AADC deficiency generally appear during the first year of life, and an infant with this disorder can experience severe developmental delay, hypotonia or weak muscle tone, difficulty moving, muscle stiffness, and athetosis or involuntary writhing movements of the limbs. The affected infant may also display lethargy or lack of energy, sleep disturbances, feeding difficulties and even behavioral issues like getting startled easily and extreme irritability. They may also experience oculogyric crises or episodes that involve abnormal rotation of the eyeballs and uncontrolled movements.
Beyond physical issues, a deficiency in AADC can also affect the other bodily processes such as blood pressure and body temperature regulation. Hence, an individual with the deficiency may also experience inappropriate or impaired sweating, constriction of the pupils, nasal congestion, drooling, low blood pressure, gastroesophageal reflux, low blood sugar or hypoglycemia, fainting, and even cardiac arrest.
Unfortunately, although medications can be prescribed to manage the symptoms, there are no approved treatments for AADC deficiency. There is, however, a way to diagnose it as early as possible.
Genetic testing in diagnosing AADC Deficiency
Genetic testing, which analyzes an individual’s genome, can detect the presence of markers associated with AADC deficiency.
It has been identified that mutations in a gene called dopa decarboxylase (DDC) cause the deficiency. Since the disorder is inherited, parents who are planning to conceive can request to undergo testing to find out whether they possess these mutations in the DDC gene and assess the risk of transmitting the disease onto their offspring.
Since the disorder runs in the family, if someone has a family member diagnosed with AADC deficiency, it is important to undergo genetic counselling right away to help determine the family’s risk and carrier status.
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