Aromatic L-amino acid decarboxylase deficiency

What causes aromatic l-amino acid decarboxylase (AADC) deficiency?

Aromatic l-amino acid decarboxylase (AADC) deficiency is caused by changes (mutations) in the DDC __gene. This gene provides instructions to the body to create an enzyme called the AADC enzyme. When this enzyme is working properly, it creates neurotransmitters called dopamine and serotonin. These neurotransmitters allow the cells of the nervous system to communicate with each other properly.

When there is a mutation in DDC , the body does not create AADC enzyme correctly, and there are not enough properly working neurotransmitters in the body. These changes therefore cause the symptoms associated with AADC deficiency.

Last updated on 05-01-20

How is aromatic l-amino acid decarboxylase (AADC) deficiency diagnosed?

Aromatic l-amino acid decarboxylase (AADC) deficiency is typically diagnosed based on a number of laboratory tests. A spinal tap may be completed to measure levels of substances related to having low levels of dopamine and serotonin. A blood sample can also be taken to measure the activity of the AADC enzyme.

If these tests are consistent with an individual having AADC deficiency, genetic testing can be completed to confirm the diagnosis. It is recommended that doctors use at least two of these methods to diagnose a person with AADC deficiency.

Last updated on 05-01-20

How is aromatic l-amino acid decarboxylase deficiency inherited?

Aromatic l-amino acid decarboxylase (AADC) deficiency is inherited in an autosomal recessive manner. This means that both copies of the DDC gene must be changed in order to have symptoms of the disease. We inherit one copy of each gene from our mother and the other from out father.

People with a mutation in only one copy of the DDC gene are known as carriers. When two carriers of AADC deficiency have children together, for each child there is a:

  • 25% chance that the child will have AADC deficiency
  • 50% chance that the child will be a carrier of AADC deficiency like the parents
  • 25% chance that the child will have two working copies of DDC , so the child will not have AADC deficiency and will not be a carrier.

Last updated on 05-01-20

What is the long-term outlook for people affected by aromatic l-amino acid decarboxylase deficiency?

There is limited information available about the long-term outlook for people diagnosed with aromatic l-amino acid decarboxylase (AADC) deficiency. There can be a wide variation in the severity of symptoms in people with the disease. It is not expected that the severity of symptoms should increase as an affected individual gets older. However, in some cases new symptoms may develop as side effects to other symptoms. For example, some people with AADC deficiency may develop joint contractures (inability to move joints) due to the movement disorders associated with the disease.

Some of the symptoms associated with AADC deficiency, such as problems controlling the autonomic nervous system, may be life-threatening in moments of stress. It is important to follow the doctor’s recommendations for monitoring the symptoms of people with AADC deficiency and to know what to do in case of an emergency.

Last updated on 05-01-20

How might aromatic L-amino acid decarboxylase deficiency (AADC) be treated?

There is currently no cure for aromatic L-amino acid decarboxylase (AADC) deficiency. Different medications can be used to help treat the signs and symptoms of the disease. However, although certain combinations of medications may help some people, there is no proven strategy that relieves the symptoms of all people with this disease. Whether or a not a treatment works may depend on the exact change in the DDC gene and how much the AADC enzyme is functioning in the body.

Since the nervous system in a child with AADC deficiency does not have enough of certain neurotransmitters, the goal of many of the treatments is to make certain as much of these neurotransmitters are available as possible.

Medication could include any one or combination of the following:

Other treatments may depend on the symptoms of each individual. These treatment options include:

Physical, occupational, and speech therapy may also be helpful in improving symptoms of the disease.

Gene therapy treatment for AADC deficiency seems promising and clinical studies in humans are currently underway.

Last updated on 05-01-20

Selected Full-Text Journal Articles

Gene therapy improves motor and mental function of aromatic l-amino acid decarboxylase deficiency.

Kojima K, Nakajima T, Taga N, et. al. Gene therapy improves motor and mental function of aromatic l-amino acid decarboxylase deficiency. Brain. 2019 Feb 1;142(2):322-333.

Last updated on 04-27-20

Name: Pediatric Neurotransmitter Disease Association 28 Prescott Place
Old Bethpage, NY, 11804, United States
Phone: 603-733-8409 Email: pnd@pndassociation.org Url: http://www.pndassoc.org/
Name: The AADC Research Trust 320 Limpsfield Road Hamsey Green
Surrey CR2 9BX
United Kingdom
Email: enquiries@aadcresearch.org Url: http://www.aadcresearch.org/
Chien YH, Chen PW, Lee NC, Hsieh WS, Chiu PC, Hwu WL, Tsai FJ, Lin SP, Chu SY, Jong YJ, and Chao MC. 3-O-methyldopa levels in newborns: Result of newborn screening for aromatic l-aminio acid decarboxylase deficiency Molecular Genetics and Metabolism. August 2016; 118(4). 259-263. Reference Link Wassenberg T, Molero-Luis M, Jeltsch K, Hoffmann G, Assmann B, Blau N, Garcia-Carzola A, Artuch R, Pons R, Pearson TS, Leuzzi V, Mastrangelo M, Pearl PL, Lee WT, Kurian MA, Heales S, Flint L, Verbeek M, Willemsen M, and Opladen T. Consensus guideline for the diagnosis and treatment of aromatic l-amino acid decarboxylase (AADC) deficiency Orphanet Journal of Rare Diseases. 2017; 12:12. Reference Link Helman G, Pappa MB, and Pearl PL. Widening Phenotypic Spectrum of AADC Deficiency, a Disorder of Dopamine and Serotonin Synthesis JIMD Reports. 2014; 17. 23-27. Reference Link

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