IVA is a rare but treatable organic acid disorder. People with organic acid disorders cannot process amino acids, the building blocks of protein.
Our body breaks down protein in food into amino acids when we eat, and breaks down protein in our muscle into amino acids during prolonged fasting and stress. Amino acids are then processed by special chemicals called enzymes so that the body can use them. Different enzymes target specifically at different amino acids.
Babies with IVA lack the specific enzyme called "Isovaleryl CoA dehydrogenase". This enzyme is responsible to process an amino acid called leucine. Whilst leucine cannot be utilized for body's use, harmful substances including isovaleric acid also build up in the body, causing health problems.
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Isovaleric Acidaemia (IVA)
Our body breaks down protein in food into amino acids when we eat, and breaks down protein in our muscle into amino acids during prolonged fasting and stress. One of the amino acids, leucine, will then be metabolized to form isovaleric acid. When functioning normally, our body will produce isovaleryl CoA dehydrogenase to metabolise leucine to produce energy for our body's use and growth. In people with IVA, isovaleryl CoA dehydrogenase is either missing or not working properly, so leucine cannot be metabolized properly. As a result, isovaleric acid and other harmful substances will build up in the body and cause serious health problems.
Everybody has two copies of genes, one from each parent, which tell the body how to make specific enzymes.
Isovaleric acidaemia is an autosomal recessive disease. Only when babies inherit two faulty copies of the gene for isovaleric acidaemia from parents, the enzyme made does not work properly or is not even made at all.
The original graphic is converted in to the following text version for your easy access to the information.
Autosomal recessive inheritance
In autosomal recessive diseases, people with two faulty copies of gene (one from father and one from mother) will develop symptoms. People with only one faulty copy of gene are be normal and they are called disease carriers. IVA is inherited in autosomal recessive manner.
If both parents are IVA carriers, for each pregnancy (no matter it is a baby boy or girl), there is a 25% (1 in 4) chance that the child has 2 copies of normal gene (who is not affected), a 50% (1 in 2) chance that the child has one normal and one faulty gene who is a carrier like the parents, and a 25% (1 in 4) chance that the child has two copies of faulty gene who is at risk for IVA.
Babies with IVA are usually healthy at birth but they can develop metabolic crisis within the first few days of life due to the build-up of toxic substances in the body.
Metabolic crisis is a period of time when a metabolic disorder makes the baby seriously ill. Babies tend to develop metabolic crisis when they do not have food for long periods of time, or when they have infection, fever, or stomach upset. Left untreated, they deteriorate with seizure and coma which can be life threatening.
Symptoms vary from person to person. Some children with IVA have very mild or no symptom, and do not develop symptoms of a metabolic crisis until they are older.
Babies with IVA benefit significantly from early treatment and can have healthy and active lives.
IVA can be treated with special diet and supplements. Some babies with mild IVA only need treatment when they are unwell. It is important to feed regularly and not to go for long periods without eating. Medication may also be given.
Babies with IVA need to see their specialist metabolic team regularly even when they do not have symptom. It is important to discuss and design a possible plan with your doctor and dietician beforehand, in order to provide extra sugary foods during illness or other times when baby is not feeding well to prevent metabolic crisis.
If you are worried that your baby is ill, it is important to follow medical advice. Bring your baby to your local accident and emergency department immediately. Take any information that you have been given about IVA, including this pamphlet, to the hospital with you.
For general queries on Newborn Screening Programme for Inborn Errors of Metabolism, please call 5741 4280 (Department of Clinical Genetics, Hospital Authority)
July 2024
Hospital Authority