Isobutyryl-CoA Dehydrogenase Deficiency
What else is it called?
- Deficiency of isobutyryl-CoA dehydrogenase
- IBD deficiency
- Isobutyryl-coenzyme A dehydrogenase deficiency
- Isobutyric Aciduria
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What causes it?
IBD deficiency is caused by mutations in the ACAD8 gene. This gene provides instructions for making the IBD enzyme which is responsible for breaking down valine (an amino acid found in many proteins). When mutations in the ACAD8 gene occur, it leads to a reduction (decrease) in the activity of the IBD enzyme or complete elimination (removal). Due to this, valine is not broken down properly which can cause reduced energy production and other symptoms associated with IBD deficiency.
How common is it?
IBD deficiency is a very rare inherited disorder. Only approximately 22 cases have been reported so far.
What are the signs and symptoms?
Most patients with IBD deficiency are asymptomatic meaning they have no signs or symptoms associated with the condition.
However, a few children with IBD deficiency have developed symptoms including:
- Dilated cardiomyopathy (weakened and enlarged heart)
- Hypotonia (weak muscle tone)
- Developmental delay
- Anaemia (low numbers of red blood cells)
- Very low blood levels of carnitine (a natural substance that helps convert certain foods into energy)
The exact range of signs and symptoms associated with this condition remain unclear as very few affected individuals have been reported.
How is it diagnosed?
Most of the patients that have been reported so far have been diagnosed through newborn screening programmes due to elevated (raised) levels of C4-carnitine as most patients appear asymptomatic.
Can it be treated?
There is currently no standard treatment for patients with IBD deficiency however, patients are encouraged to work with a metabolic disease specialist and a dietician experienced in metabolic disorders.
Treatments that may be recommended for some babies and children with IBD are:
- Taking L-carnitine (a safe a natural substance which helps the body’s cells make energy and get rid of harmful wastes). This can also help with preventing or treating heart problems and anaemia seen in individuals with IBD deficiency.
- Avoid fasting – Fasting (going without food for a long time) can cause the body to its fat and protein stores which can lead to a build-up of harmful substances in the blood. Eating every 4 to 6 hours may avoid this in these individuals.
- Low valine diet- Most individuals with IBD deficiency do not require a change in diet however, for some patients a low-valine diet may be necessary. Valine is found in all foods with protein such as dairy products, meat, fish eggs, beans, nuts etc. Please make sure you are advised and monitored by a dietician or physician before making any changes to your diet.
Some treatments may be encouraged even without symptoms present. Treatment may be necessary throughout life.
Do my family need to be tested?
IBD deficiency is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents.
The pattern of inheritance of IBD deficiency is autosomal recessive. This means that carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with IBD deficiency are carriers.
When both parents are carriers, the risk to the baby in each pregnancy is
- 25% chance (1 in 4) of developing the condition
- 50% chance (1 in 2) for the baby to be a carrier of the condition
- 25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier
Genetic counselling can be requested to get a full explanation.