Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare inherited condition in which the communication between the brain and other parts of the body is impaired. Symptoms such as weak muscle tone (hypotonia) and autonomic dysfunction usually appear in early infancy.

Autonomic function refers to bodily and organ functions such as heart and respiratory rate, blood pressure, digestion, and pupillary response.

Causes of autonomic dysfunction

AADC deficiency is caused by a mutation in the dopa decarboxylase (DDC) gene. The DDC gene provides the instructions necessary to build the L-amino acid decarboxylase enzyme. This enzyme performs the last step in the biosynthesis of the neurotransmitters dopamine and serotonin. Neurotransmitters are signaling molecules that enable the communication between nerve cells in the brain and other parts of the body. Peripheral nerves (those outside the brain) control not only muscle movements but also autonomic functions.

Mutations in the DDC gene lead to either reduced production of the L-amino acid decarboxylase enzyme or decreased activity of the enzyme. In both cases, serotonin and dopamine levels are lowered, resulting in both autonomic dysfunction and movement disorders.

Symptoms

Autonomic dysfunction in AADC deficiency may cause the following symptoms:

  • Low blood pressure
  • Increased or decreased sweating
  • Difficulties in controlling body temperature
  • Drooping eyelids
  • Drooling
  • Nasal congestion
  • Gastroesophageal reflux disease (backflow of acid from the stomach to the esophagus)
  • Constriction of the pupils of the eyes (miosis)
  • Fainting (syncope)
  • Deregulated heart rate
  • Gastrointestinal problems (constipation, diarrhea)
  • Cardiac arrest

Treatment options

Treatment of autonomic dysfunction in AADC deficiency is not well established. According to case reports, the vasoconstrictor (agent that constricts the blood vessels) oxymetazoline can help to relieve nasal congestion. Anticholinergic agents, such as trihexyphenidyl, may improve sweating. Fundoplication surgery or GERD surgery can improve gastroesophageal reflux. Gastrointestinal medications can help to relieve digestive problems such as constipation and diarrhea.

 

Last updated: Sept. 26, 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.

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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.