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
What causes medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency?
MCADD is caused by mutations in the
ACADM gene. This gene gives the body instructions for making an enzyme called medium-chain acyl-CoA dehydrogenase, needed to break down fats called medium-chain fatty acids. These fatty acids are found in foods and the body's
tissues, and are an important source of energy for the heart, muscles, liver, and other tissues. Mutations in this gene lead to low levels of the enzyme, which means that medium-chain fatty acids are not broken down properly. They cannot be converted to energy, leading to the symptoms of MCADD.
[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
How is medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency inherited?
Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) is inherited in an
autosomal recessive manner.
[1] This means that to have MCADD, a person must have a
mutation in both copies of the responsible
gene in each
cell. There is nothing either parent can do, before or during a pregnancy, to cause a child to have this condition.
People with MCADD inherit one mutation from each of their parents. The parents, who each have one mutation, are known as
carriers. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When 2 carriers of an autosomal recessive condition have children, each child has a:
- 25% chance to have the condition
- 50% chance to be an unaffected carrier like each parent
- 25% chance to be unaffected and not a carrier
Last updated: 8/29/2017
What risks are posed to other members of an affected individual's family?
The risk to other family members depends on the status of the individuals most closely related to the affected individual. At conception, the siblings of an affected individual have a 25% risk of being affected, a 50% risk of being asymptomatic carriers, and a 25% risk of being unaffected and not carriers. The risk could be 50% if one of the parents is also affected. Because asymptomatic parents and siblings may have MCAD deficiency, biochemical evaluation and/or molecular genetic testing should be offered to both parents and all siblings.
[4]
Last updated: 6/7/2016
Where can I learn more about the risks posed to my family members and the importance of genetic testing?
Your family may benefit from consulting with a genetics professional who can help to determine who may be at risk for medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency and who warrants further testing.
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.
