Glutaric Aciduria Type 1
What else is it called?
- GA 1
- Glutaryl-CoA Dehydrogenase Deficiency
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What causes it?
Glutaric Aciduria Type 1 (GA1) is a rare inherited metabolic disorder. Glutaric Aciduria means there is too much glutaric acid in the blood and urine. Metabolism refers to the chemical processes that occur inside the cells of the body.
GA1 affects the way your body breaks down protein. Many foods contain protein and your body needs it for growth and repair.
Protein is broken down into amino acids (the building blocks of protein) by enzymes (which are like chemical scissors). Enzymes then further break the amino acids into smaller parts.
In GA1, the body lacks an enzyme called glutaryl-CoA dehydrogenase. This means that the body is unable to break down two amino acids called lysine and tryptophan. This leads to a build-up of glutaric acid.
GA1 is a serious inherited metabolic disorder that can lead to severe movement problems. Children are very vulnerable in the first 6 years of life. Damage can be prevented with a protein-restricted diet, a protein substitute and carnitine.
How common is it?
Around 1 in 100,000 children worldwide are thought to be affected by GA1.
What are the signs and symptoms?
The basal ganglia in the brain controls movement. The build-up of glutaric acid damages the basal ganglia and causes movement problems.
A metabolic crisis can trigger the movement problems. This is because there is a build-up of glutaric acid and other toxic chemicals. It is usually caused by childhood infections or viruses causing high temperatures, vomiting and diarrhoea. Avoidance of a metabolic crisis is essential.
Babies with GA1 are usually healthy at birth although many are born with a larger than average head size.
How is it diagnosed?
GA1 is diagnosed by newborn screening. High levels of glutaric acid are found in the blood.
Can it be treated?
GA1 is managed with the following special diet and medication:
- A protein-restricted diet
- A protein substitute
- Carnitine medication
In GA1, it is important that enough protein is given for growth… but not too much as toxic chemicals will be made.
In babies, a restricted amount of protein is given from breast milk or measured amounts of infant formula. The amount given will be monitored regularly by your specialist metabolic dietitian.
Protein substitute is essential for metabolic control. It will help to meet your baby’s protein, energy, vitamin and mineral requirements. It is available on prescription.
During any childhood illness, an emergency regimen is given. Illnesses can cause catabolism or protein breakdown. This will lead to a build-up of glutaric acid and cause a metabolic crisis.
During illness, you should:
- Stop all protein in food and drink
- Start the emergency regimen. This is made up of protein substitute and glucose polymer
- Use carnitine medication as prescribed
- Phone your metabolic team
Always take full amounts of emergency feeds as prescribed. If symptoms continue and/or you are worried, go immediately to the hospital. Regularly update your metabolic team
It is imperative that emergency feeds are started promptly and there are no delays in management.
GA 1 is monitored using:
- Frequent blood tests to check amino acid and nutrient levels
- Height and weight
- Developmental checks
Diet and medications are adjusted according to age, weight and blood chemical levels.
With good management, severe movement problems can be prevented in the majority of children.
- Always ensure you have a good supply of your dietary products and medicines and that they are in date.
- Your dietary products and medications are prescribed by your GP. These are obtained via a pharmacy or home delivery.
- Always ensure you have your emergency feed products and a written emergency plan.
- Medications to control fever should be given as normally recommended – always keep supplies available.
Do my family need to be tested?
Humans have chromosomes composed of DNA. Genes are pieces of DNA that carry the genetic instruction. Each chromosome may have several thousand genes.
The word mutation means a change or error in the genetic instruction.
We inherit particular chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instruction that determines characteristics, which are a combination of the parents.
GA1 is an inherited condition. There is nothing that could have been done to prevent your baby from having GA1.
Everyone has a pair of genes that make the glutaryl-CoA dehydrogenase enzyme. In children with GA1, neither of these genes works correctly. These children inherit one non-working GA1 gene from each parent.
Parents of children with GA1 are carriers of the condition. Carriers do not have GA1 because the other gene of this pair is working correctly.
When both parents are carriers, in each pregnancy the risk to the baby is as follows:
- There is a 25% chance (1 in 4) of the baby having GA1.
- There is a 50% chance (1 in 2) for the baby to be a carrier of GA1
- There is a 25% chance (1 in 4) for the baby to have two working genes and neither have GA1