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Genetic and Rare Diseases Information Center (GARD)

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Medium-chain acyl-coenzyme A dehydrogenase deficiency


Other Names for this Disease

  • ACADM deficiency
  • Acyl-CoA dehydrogenase medium chain deficiency of
  • MCAD deficiency
  • MCADD
  • MCADH deficiency
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

My sister's daughter (my niece) recently had a baby and he was diagnosed with medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency. If this condition is traced back to my sister, is it important for me and/or my children (ages 8 and 11) to be tested? 

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

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). Normally, through a process called fatty acid oxidation, several enzymes work in a step-wise fashion to break down (metabolize) fats and convert them to energy. People with MCADD do not have enough of an enzyme needed for the step that metabolizes a group of fats called medium-chain fatty acids. MCADD is caused by mutations in the ACADM gene and is inherited in an autosomal recessive manner.[1] Treatment includes avoidance of fasting and of medium chain triglycerides in the diet.[2]
Last updated: 7/7/2014

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: 7/7/2014

What causes medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency?

Mutations in the ACADM gene cause medium-chain acyl-coenzyme A dehydrogenase deficiency. Mutations in the ACADM gene lead to inadequate levels of an enzyme called medium-chain acyl-coenzyme A dehydrogenase. Without sufficient amounts of this enzyme, medium-chain fatty acids from food and fats stored in the body are not metabolized properly. As a result, these fats are not converted to energy, which can lead to characteristic signs and symptoms of this disorder such as lethargy and low blood sugar. Medium-chain fatty acids or partially metabolized fatty acids may accumulate in tissues and can damage the liver and brain, causing serious complications.[1]
Last updated: 2/4/2011

How is medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) diagnosed?

MCADD is now included in many newborn screening programs. If a newborn screening result for MCADD is not in the normal range, additional testing is recommended. A diagnosis of MCADD can be made through a blood test called a plasma acylcarnitine profile and an evaluation of organic acids in the urine. The diagnosis can also be confirmed by genetic testing.[2]
Last updated: 7/7/2014

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. This means that both copies of the responsible gene in each cell must have mutations for a person to be affected. Usually, the parents of a person with an autosomal recessive condition each have one mutated copy of the gene and are referred to as carriers. Carriers typically do not have any signs or symptoms of the condition.[1]

When two carriers of an autosomal recessive condition have children, each child has a 25% (1 in 4) chance to be affected, a 50% (1 in 2) chance to be a carrier like each parent, and a 25% chance to be unaffected and not be a carrier.
Last updated: 7/7/2014

What risks are posed to other members of an affected individual's family?

At conception, the sibs 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 sibs may have MCAD deficiency, biochemical evaluation and/or molecular genetic testing should be offered to both parents and all sibs.[3] The risk to other family members depends on the status of the individuals most closely related to the affected individual. 
Last updated: 12/11/2008

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. Genetics clinics are a source of information for individuals and families regarding genetic diagnosis, natural history, treatment, mode of inheritance, and genetic risks to other family members. To find a genetics clinic, we recommend that you contact your primary doctor for a referral. Click here to learn more about genetic consultations. 

The following online resources can also help you find a genetics professional in your community:

  * GeneTests - A searchable directory of US and international genetics and prenatal diagnosis clinics. Go to the following link and click on 'Clinic Directory' to find a genetic service close to you.
http://www.geneclinics.org/

  * ResourceLink - A database of genetics counseling services, searchable by location, name, institution, type of practice, or specialty. Hosted by the National Society of Genetic Counselors.
http://www.nsgc.org/resourcelink.cfm

  * Genetic Centers, Clinics, and Departments - A comprehensive resource list for genetic counseling, including links to genetic centers and clinics, associations, and university genetics departments. Hosted by the University of Kansas Medical Center.
http://www.kumc.edu/gec/prof/genecntr.html

Last updated: 12/11/2008

References
Other Names for this Disease
  • ACADM deficiency
  • Acyl-CoA dehydrogenase medium chain deficiency of
  • MCAD deficiency
  • MCADD
  • MCADH deficiency
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.