Aromatic l-amino acid decarboxylase (AADC) deficiency is a rare disease caused by genetic mutations. Patients with AADC deficiency display muscle weakness early in life. The symptoms of AADC deficiency also include muscle spasms, drops in blood pressure, and cardiac arrest in severe cases. Patients can also have developmental delays, meaning that they are slow in learning to crawl and walk.
There is currently no cure for AADC deficiency, but there are treatments available to alleviate some of the symptoms and improve patients’ quality of life.
What causes AADC deficiency?
AADC deficiency is caused by mutations in the DDC gene, which provides instructions for making a key enzyme. Without this enzyme, nerve cells cannot produce the signaling molecules that make communication between nerve cells in the brain and between the brain and other organs and tissues possible. These signaling molecules, or neurotransmitters, include dopamine and serotonin and are found in very low levels in the brains of patients with AADC deficiency.
Vitamin B6 (pyridoxine)
The first treatment for patients with AADC deficiency is vitamin B6, also called pyridoxine. Vitamin B6 acts as a cofactor of the AADC enzyme — in cases where patients have small amounts of functional AADC enzyme, this treatment can increase the activity of the enzyme that is present. However, several case studies have indicated that this treatment leads to only limited improvements in AADC deficiency patients.
Dopamine receptor agonists
Dopamine receptor agonists are compounds that bind to dopamine receptors in the brain, activating the receptors. In some conditions, dopamine receptor agonists can compensate for a decrease in dopamine in the brain. While no dopamine receptor agonists have been approved to treat AADC deficiency, this type of medication has been used off-label for this disease. Dopamine receptor agonists include bromocriptine, rotigotine, and aripiprazole, among others.
Monoamine oxidase inhibitors (MAOIs)
Monoamine oxidase inhibitors (MAOIs) are a class of medications that inhibit MAO, the enzyme that breaks down serotonin and dopamine. They, therefore, act to increase the amount of dopamine and serotonin in the brain. Even though MAOIs have not been approved to treat AADC deficiency, they have been prescribed off-label to treat some AADC patients. However, there is limited evidence that MAOIs are effective in treating the symptoms of AADC deficiency.
Several companies (including PTC Therapeutics) are developing gene therapies to treat AADC deficiency. This type of experimental treatment uses a virus to introduce a corrected version of the DDC gene into nerve cells so that they can produce normal AADC enzyme.
Physiotherapy is the use of physical methods to treat a disease or injury. Physical therapists can design an exercise regimen to help patients build muscle strength and dexterity safely. They can prescribe exercises to improve range of motion and flexibility, as well as working with patients to overcome the specific problems that they might face.
Much like physical therapists, occupational therapists can help patients find easier ways to perform daily tasks, such as getting dressed or feeding themselves. Occupational therapists can also prescribe adaptive devices. This might be something as simple as a foam handle to make a toothbrush easier to grasp, or something more complex, like an orthotic brace to make walking easier.
Patients with AADC deficiency often have difficulty suckling and swallowing. Speech therapists can work with patients and prescribe specific exercises to strengthen the muscles of the throat, jaw, and mouth to make eating and speaking easier.
Some patients may need to work with a dietitian to ensure that they are getting the nutrients they need, even if they are not able to eat as much.
Last updated: Sept. 10, 2019
AADC News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.