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What is AADC Deficiency?

AADC deficiency is a rare genetic disorder that affects the brain, causes weak muscle tone, and affects how a child develops

“My hope for families, for the children and the families, is that we will recognize these children sooner.”
Warren A. Marks, MD
gene

First, it’s important to know that genetic disorders are caused by a change or alteration (mutation) in genes.

Genes:

  • Are found within cells
  • Are made up of DNA
  • Carry information that determines what traits and characteristics are passed down to individuals from their parents and that can influence how a person looks, including skin, hair, and eye color
  • Provide instructions on making proteins, including enzymes, which carry out many functions in cells in the body

Sometimes an altered gene can lead to genetic health problems or disorders, like Aromatic L-amino Acid Decarboxylase (AADC) deficiency.

A gene in the body called the dopa decarboxylase (DDC) gene is needed to make an enzyme called AADC. The AADC enzyme helps to make natural chemicals called neurotransmitters.

Neurotransmitters

Neurotransmitters are messages that are sent between cells, called neurons, in the nervous system. These messages are important because they help to control many of the body’s functions.

gene

AADC deficiency is a disorder that interferes with the way the cells in the nervous system talk to each other.

Enzymes
Enzymes
  • In AADC deficiency, a change (mutation) within the DDC gene leads to a decrease in, or no activity of, the AADC enzyme
  • This results in a lower level of neurotransmitters
  • Without enough neurotransmitters (messages), neurons can’t communicate with each other
  • This means the body can’t perform important functions, which can result in the symptoms of AADC deficiency that limit daily life

Because some neurotransmitter levels are very low in children with AADC deficiency, this condition is considered part of a broader group of genetic disorders called neurotransmitter disorders.

How AADC deficiency is passed down

Our genes come from our parents. Each person gets 2 copies of every gene, 1 from each parent. These copies of genes can be working copies, or copies that do not work as they are supposed to (altered or mutated copies).

AADC deficiency is inherited, or passed down, from a person’s parents. In order for a person to have AADC deficiency, both the mother and father must carry an altered (mutated) copy of the DDC gene. Each parent then has to pass down 1 altered copy of the DDC gene to the child, so the child has 2 altered copies.

This is an autosomal recessive disorder, or a disorder that occurs when 2 altered copies of a gene are passed down to the child: 1 from the mother and 1 from the father.

“At 3 months, we started to worry, because [our daughter] didn’t hold her head up; she laid on her stomach and almost never lifted her head. She was generally very inactive and had trouble sleeping.”
Viktoria Shamrin, mother and caregiver of Daria
Viktoria Shamrin
doctor

Doctor Information Sheet

Print out an Information Sheet to give to your child’s doctor that explains the signs, symptoms, and diagnostic tests for AADC deficiency.

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