The following information may help to address your question:
What is medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency?
Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) is an
inherited metabolic disorder that prevents the body from converting certain fats to energy, particularly during periods without food (fasting). People with MCADD do not have enough of an
enzyme needed to metabolize a group of fats called medium-chain fatty acids. Signs and symptoms usually begin by early childhood and may include vomiting, lack of energy, and
low blood sugar (hypoglycemia). Symptoms can be triggered by periods of fasting or by illnesses.
[1]
MCADD is caused by
mutations in the
ACADM gene and inheritance is
autosomal recessive.
[1] Treatment includes strict avoidance of fasting and avoidance of medium chain triglycerides in the diet.
[2] If not treated, people with MCADD are at risk of serious complications including sudden death.
[1]
Last updated: 8/29/2017
What are the signs and symptoms of medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency?
The initial signs and symptoms of medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) typically occur during infancy or early childhood and can include vomiting, lack of energy (lethargy), and low blood sugar (hypoglycemia). In rare cases, the first episode of problems related to MCADD occurs during adulthood. The signs and symptoms of MCADD can be triggered by periods of fasting, or during illnesses such as viral infections, particularly when eating is reduced. People with MCADD are also at risk of serious complications such as
seizures, breathing difficulties, liver problems, brain damage, coma, and sudden, unexpected death.
[1]
Last updated: 8/29/2017
How is medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) diagnosed?
A diagnosis of MCADD requires an evaluation of a person's symptoms as well as the interpretation of several tests. Initial testing may include:
- Plasma acylcarnitine
- Urine organic acid
- Urine acylglycine
Further testing to confirm the diagnosis may include molecular
genetic testing of the
ACADM gene or biochemical genetic testing.
[3]
MCADD is included in many
newborn screening programs, so a newborn with MCADD who does not yet exhibit symptoms may be diagnosed early. If a
newborn screening result for MCADD is not in the normal range ("positive"), additional testing can then be ordered.
[2]
Last updated: 8/29/2017
What is newborn screening?
Newborn
screening tests look for serious developmental, genetic, and metabolic disorders so that important action can be taken during the critical time before symptoms develop.
Screening tests do not diagnose illnesses. They identify which babies need additional testing to confirm or rule out illnesses. Good screening tests have a low false-negative rate (if the test is normal, the child should be healthy), but may have a high false-positive rate (as many affected children as possible should test positive, even if this means many healthy children also test positive).[4]
An abnormal result on a newborn screen means that the child should have additional testing to confirm or rule out the condition. If a disorder is diagnosed on follow-up testing, appropriate treatment can be started right away, before symptoms appear.[4]
Last updated: 6/7/2016
Are there factors which can cause a false positive test result for medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency on newborn screen?
The false positive rate for medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency varies between screening programs because of differences in analysis of acylcarnitine (a type of fatty acid). Programs that screen for MCAD deficiency but not other fatty acid oxidation disorders often limit their analysis to octanoylcarnitine, the primary screening
marker for MCAD deficiency. However, octanoylcarnitine is not specific for MCAD deficiency and is expected to be elevated in several other disorders including
glutaric acidemia type II. Consideration of other potential disorders in the
differential diagnosis should minimize the false positive rate.
[5]
Last updated: 6/7/2016
What follow-up testing can be done to definitively determine if my child has medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency?
ACADM is the only
gene known to be associated with medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency. The biochemical diagnosis of MCAD deficiency can be confirmed by measurement of MCAD enzyme activity in
fibroblasts or other
tissues and/or by genetic testing to detect
mutations in the
ACADM gene.
[5]
For more information on genetic testing for MCAD deficiency, we would recommend you consult with a genetics professional.
Last updated: 6/7/2016
How can I find a genetics professional in my area?
Last updated: 8/23/2016
We hope this information is helpful. We strongly recommend you discuss this information with your doctor. If you still have questions, please
contact us.
Warm regards,
GARD Information Specialist
Please see our Disclaimer.
