What else is it called?
- 3-Hydroxy-isobutyryl-CoA hydrolase deficiency
- Neurodegeneration due to 3-hydroxyisobutyryl-CoA hydrolase deficiency
- HIBCH deficiency
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What causes it?
Methacrylic aciduria is a rare mitochondrial disease caused by 3-Hydroxy-isobutyryl-CoA hydrolase (HIBCH) gene mutations. The mitochondria are the energy production centre of the cell. The HIBCH gene gives instructions to produce a mitochondrial enzyme involved with the amino acid valine, leucine and isoleucine metabolism pathways.
As a result, toxic valine, leucine and isoleucine metabolites build up in the body. More specifically, these toxic metabolites build up within the mitochondria of the body’s cells which may be harmful to your son or daughters health.
How common is it?
The vast majority of reported cases involved the Iraqi-Jewish population, in which the prevalence of the disorder has been estimated at around 1 in 10 000. Currently, it is unclear whether this condition is more common in males or females.
What are the signs and symptoms?
Symptoms of this condition usually present within the first stages of life. From previous research, individuals diagnosed with this condition tend to display signs and symptoms of:
- Delayed development of motor skills
- Poor muscle tone
- Initial poor feeding
- Deterioration in neurological function from birth
However, it is worth noting your child may or may not experience all of these symptoms although these are the most common.
How is it diagnosed?
HIBCH deficiency may take a while to diagnose as symptoms are similar to another disease, called Leigh syndrome. Diagnosis is aided by blood tests which show high levels of lactic acid, and imaging studies via an MRI scan which show changes in the “globi pallidi” structure of the brain.
Magnetic resonance imaging (MRI) is a type of scan that uses strong magnetic fields and radio waves to produce detailed images of the inside of the body. The MRI scanner is operated by a radiographer, who is trained in carrying out imaging investigations. They control the scanner using a computer, which is in a different room, to keep it away from the magnetic field generated by the scanner. You will be able to talk to the radiographer through an intercom and they’ll be able to see you on a television monitor throughout the scan. At certain times during the scan, the scanner will make loud tapping noises. This is the electric current in the scanner coils being turned on and off. You’ll be given earplugs or headphones to wear.
Can it be treated?
Currently, there is not a cure for HIBCH deficiency. Children with HIBCH deficiency require a multidisciplinary team of doctors who can assess how the deficiency is affecting each body system and recommend appropriate treatments.
Do my family need to be tested?
HIBCH deficiency can only be passed on to a child if both parents have a copy of the faulty gene. This is called autosomal recessive inheritance. A person who has a copy of the faulty gene is known as a carrier.
If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have.
If the child only inherits one copy of the faulty gene, they will be a carrier but will not have the disorder. In some rare cases, carriers have had mild symptoms of the disorder for which they carry the faulty gene.
Once you are diagnosed, you can speak to a genetic counsellor. They can explain how you may have inherited HIBCH deficiency. They can also tell you about genetic testing for the rest of your family. They can provide advice and support if you go on to have children of your own. If you have previously had a child with HIBCH deficiency and go on to have further children, their New-born Screening test should be carried out within 24-48 hours of birth.