The True Number of AADC Deficiency Patients

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by Richard E. Poulin III |

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Earlier this year, CheckRare, a learning platform for healthcare professionals and rare disease patients, held a panel discussion about the rare disease aromatic l-amino decarboxylase (AADC) deficiency.

The panel featured five leading experts in pediatric neurology and movement disorders, including two doctors I have spoken with directly. Paul Wuh-Liang Hwu, MD, PhD, is a professor in pediatrics and medical genetics at National Taiwan University Hospital, and Irina A. Anselm, MD, is the director of the mitochondrial program and the co-director of the neurometabolic program at Boston Children’s Hospital and an assistant professor of neurology at Harvard Medical School. I have always benefited from their insight and was excited to see them connect with other experts.

The panelists’ experience with AADC deficiency is particularly impressive, given that there are so few patients to learn from. A 2020 article in the Journal of Inherited Metabolic Disease notes that only about 135 cases have been described worldwide since 1990. That’s why I was surprised when Anselm shared that the incidence of AADC deficiency is actually much higher. Although studies have estimated different birth rates, Anselm said our community may potentially total about 1,800 patients.

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Because AADC deficiency is so rare, it makes sense that there are more patients out there who are undiagnosed or misdiagnosed. The symptoms of AADC deficiency can mimic those of cerebral palsy, and many in our community have shared stories about being misdiagnosed. I believed there could be as many as 100 more patients out there, but hundreds more far exceeds my estimates.

If there are truly 1,800 AADC deficiency patients, then improvements in diagnostic testing and newborn screening should help to identify more. It’s why members of our community contributed to a recent column of mine that was aimed at parents researching symptoms of their child’s undiagnosed disease.

Although children with AADC deficiency typically don’t present clear symptoms in the first few months of life, creating more awareness of the disease can help doctors recognize unspecific symptoms and the class of diseases they might fall under.

Those who are undiagnosed or think they may have been misdiagnosed would benefit from a blood test or a lumbar puncture. These relatively minimally invasive tests will quickly identify biomarkers that indicate if a child has AADC deficiency. Genetic testing is also helpful, but it takes more time to receive the results.

AADC deficiency prevalence | AADC News | Richard, his wife, Judy, and their daughter, Rylae-Ann, travel to Taiwan seeking a diagnosis. Richard and Judy are both smiling and wearing black jackets, while Rylae-Ann, then a baby, wears a pink coat and hat.

From left, Judy, Rylae-Ann, and Richard visit a professor in Taiwan with AADC deficiency experience. They receive a quick diagnosis. (Photo by Richard E. Poulin III)

My wife, Judy, and I visited more than five specialists to determine what condition my daughter has. After extensive testing, none were able to offer a diagnosis. We had a hunch our daughter had AADC deficiency, so we scheduled an appointment with Dr. Hwu after reading his research papers about the disease.

During our first meeting, he was able to diagnose Rylae-Ann after a quick observation. This demonstrates that AADC deficiency isn’t always difficult to diagnose. The greater problem is the lack of awareness. It’s currently difficult to find doctors who have experience with AADC deficiency, but everyone in our community can share information and spread awareness.

Note: 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. The opinions expressed in this column are not those of AADC News or its parent company, BioNews, and are intended to spark discussion about issues pertaining to aromatic l-amino acid decarboxylase deficiency.