Aromatic l-amino acid decarboxylase (AADC) deficiency is a genetic and neurometabolic disease whose symptoms usually manifest in early infancy. It affects the nervous system and hinders the ability of its cells to communicate with the body.

Causes

Neurotransmitters are signaling molecules that mediate communication between the brain and the rest of the body through the nerve cells. Their production and proper functioning are crucial for the development and correct metabolic workings of the body.

AACD deficiency is caused by mutations in the DDC gene, which carries the instructions necessary to make the aromatic l-amino acid decarboxylase or the AADC enzyme. This enzyme is vital for the production of dopamine and serotonin, two very important neurotransmitters. Mutations in the DDC gene lead to low and insufficient levels of the AADC enzyme being produced, affecting the production of dopamine and serotonin, and impeding communication between the brain and other organs.

Symptoms

The symptoms of AADC deficiency and their severity vary from person to person. They include those caused by developmental delays, and those due to the impact of AADC’s loss on the autonomic nervous system, which controls processes like blood pressure that are beyond conscious effort. Disease symptoms can include:

  • weak muscle tone (hypotonia)
  • painful muscle stiffness
  • uncontrollable movement of the hands and legs.
  • low blood pressure (hypotension)
  • fainting
  • low blood sugar (hypoglycemia)
  • impaired sweating
  • abnormal weight gain
  • inability to regulate body temperature
  • vision problems (droopy eyelids and pupil constriction)
  • cardiac arrest

Symptoms of AADC can lead to a lack of energy, difficulties with eating, and sleep problems.

Diagnosis

A doctor will perform a detailed review of the child’s medical history and symptoms. Based on these, a blood test is often taken to measure levels of the AADC enzyme. A spinal tap or lumbar puncture to collect cerebrospinal fluid (CSF) may also be undertaken. Levels of dopamine and serotonin in the CSF can help to diagnose AADC deficiency.

Genetic testing can also be performed to detect mutations in the DDC gene and confirm the diagnosis.

Treatment

AADC deficiency treatments focus on managing its symptoms. Medications that mimic the function of dopamine (dopamine receptor agonists), prevent the breakdown of dopamine and serotonin (monoamine oxidase inhibitors), and vitamins like pyridoxine or vitamin B6 are commonly used. Other treatments, such as those to treat stomach problems, sleep issues, and seizures, may also be prescribed depending on a patient’s needs.

Gene therapy is a promising option as a potential treatment of AADC deficiency. However, the approach is in its early stages of development and still under investigation.

Patients with AADC deficiency can also benefit from physical and occupational therapy, like that given to improve muscle strength and flexibility, performed under the guidance of trained specialists.

 

Last updated: September 8, 2019

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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 healthcare providers 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.

Vijaya Iyer is a freelance science writer for BioNews Services. She has contributed content to their several disease-specific websites, including cystic fibrosis, multiple sclerosis, muscular dystrophy, among others. She holds a PhD in Microbiology from Kansas State University, where her research focused on molecular biology, bacterial interactions, metabolism, and animal models to study bacterial infections. Following the completion of her PhD, Dr. Iyer went on to complete three postdoctoral fellowships at Kansas State University, University of Miami and Temple University. She joined BioNews Services to utilize her scientific background and writing skills to help patients and caregivers remain abreast with important scientific breakthroughs.
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Özge has a MSc. in Molecular Genetics from the University of Leicester and a PhD in Developmental Biology from Queen Mary University of London. She worked as a Post-doctoral Research Associate at the University of Leicester for six years in the field of Behavioural Neurology before moving into science communication. She worked as the Research Communication Officer at a London based charity for almost two years.
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Vijaya Iyer is a freelance science writer for BioNews Services. She has contributed content to their several disease-specific websites, including cystic fibrosis, multiple sclerosis, muscular dystrophy, among others. She holds a PhD in Microbiology from Kansas State University, where her research focused on molecular biology, bacterial interactions, metabolism, and animal models to study bacterial infections. Following the completion of her PhD, Dr. Iyer went on to complete three postdoctoral fellowships at Kansas State University, University of Miami and Temple University. She joined BioNews Services to utilize her scientific background and writing skills to help patients and caregivers remain abreast with important scientific breakthroughs.
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