Common Misdiagnoses of AADC Deficiency

Common Misdiagnoses of AADC Deficiency
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Only about 100 cases of aromatic l-amino acid decarboxylase (AADC) deficiency are reported in scientific literature globally. This is partly because some individuals are wrongly diagnosed with cerebral palsy or other neurological conditions.

Here are some reasons for the misdiagnoses that commonly accompany AADC deficiency.

What is AADC deficiency?

AADC deficiency is a genetic neurometabolic disease, symptoms of which usually emerge in early infancy. The cause is mutations in the DDC gene, which carries the instructions for cells to make the AADC enzyme. This enzyme is crucial for the production of two important neurotransmittersdopamine and serotonin, from other molecules. Because of the mutations in the DDC gene, cells fail to produce sufficient levels of dopamine and serotonin, affecting the ability of nerve cells to communicate with each other and the rest of the body. The disease affects many aspects of a person’s life.

The diagnostic journey

Tests to confirm AADC deficiency include measuring dopamine and serotonin levels in the cerebrospinal fluid. Others may involve testing the activity of the AADC enzyme in the blood, and analyzing the DDC gene for mutations.

However, AADC deficiency is difficult to diagnose because its symptoms are similar to those of other disorders, and many physicians are unfamiliar with the disease. Patients may have developmental delays, weak muscle tone, muscle stiffness, and athetosis (involuntary jerking of limbs). Other symptoms can include unusual eye movements, droopy eyelids, and excessive sweating.

Although symptoms often become evident in infancy, an accurate diagnosis may take a long time, and several specialists may need to see your child before they reach a diagnosis. The age range of diagnosis is two months to 23 years.

Conditions with symptoms that mimic AADC deficiency

Disorders with symptoms similar to AADC deficiency include epilepsy, cerebral palsy, mitochondrial disease, and neuromuscular weakness.

There are ways to differentiate among these conditions, however. For example, patients with AADC deficiency have oculogyric crises, which doctors often attribute to seizure disorders. But people with a seizure have abnormal electroencephalogram (EEG) results, while those with AADC deficiency generally do not.

Likewise, magnetic resonance imaging (MRI) results are abnormal in cerebral palsy and very slight in AADC deficiency. Still, dystonia (involuntary muscle contractions), rigidity, and motor development delays in AADC deficiency are commonly misdiagnosed as symptoms of cerebral palsy.

Finally, symptoms of muscle weakness, akinesia (frozen movement), and droopy eyes in AADC deficiency are sometimes wrongly attributed to neuromuscular weakness.

Why is the correct diagnosis important?

The sooner a person receives an accurate diagnosis, the sooner treatment can start.

Identifying the underlying genetic mutations causing AADC deficiency is also key to understanding the nature of an individual patient’s disease and likely outcomes (prognosis).

What can I do to get a correct diagnosis?

If your child has AADC deficiency symptoms, consider speaking with his or her doctor about testing for the disorder. Also, if your child has had multiple tests but you still don’t have a diagnosis, ask your doctor about testing for AADC deficiency.

 

Last updated: Sept. 30, 2020

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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.

Mary M. Chapman began her professional career at United Press International, running both print and broadcast desks. She then became a Michigan correspondent for what is now Bloomberg BNA, where she mainly covered the automotive industry plus legal, tax and regulatory issues. A member of the Automotive Press Association and one of a relatively small number of women on the car beat, Chapman has discussed the automotive industry multiple times of National Public Radio, and in 2014 was selected as an honorary judge at the prestigious Cobble Beach Concours d’Elegance. She has written for numerous national outlets including Time, People, Al-Jazeera America, Fortune, Daily Beast, MSN.com, Newsweek, The Detroit News and Detroit Free Press. The winner of the Society of Professional Journalists award for outstanding reporting, Chapman has had dozens of articles in The New York Times, including two on the coveted front page. She has completed a manuscript about centenarian car enthusiast Margaret Dunning, titled “Belle of the Concours.”
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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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Mary M. Chapman began her professional career at United Press International, running both print and broadcast desks. She then became a Michigan correspondent for what is now Bloomberg BNA, where she mainly covered the automotive industry plus legal, tax and regulatory issues. A member of the Automotive Press Association and one of a relatively small number of women on the car beat, Chapman has discussed the automotive industry multiple times of National Public Radio, and in 2014 was selected as an honorary judge at the prestigious Cobble Beach Concours d’Elegance. She has written for numerous national outlets including Time, People, Al-Jazeera America, Fortune, Daily Beast, MSN.com, Newsweek, The Detroit News and Detroit Free Press. The winner of the Society of Professional Journalists award for outstanding reporting, Chapman has had dozens of articles in The New York Times, including two on the coveted front page. She has completed a manuscript about centenarian car enthusiast Margaret Dunning, titled “Belle of the Concours.”
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