Acyl-coa dehydrogenase, medium-chain, deficiency of

Diagnosis and Testing

How do I get tested for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Most people with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency are diagnosed after a positive result from newborn screening. During routine newborn screening, a tiny sample of blood is taken from the heel of a newborn. This test called a heel prick or Guthrie test involves getting a few drops of blood from a pinprick in the newborn's heel. The blood is run through a machine that can detect high levels of acylcarnitines, a substance that abnormally builds up in people with MCAD deficiency. Sometimes, newborn screening may miss an infant with MCAD deficiency, and sometimes there may be a false positive.

Additional tests will be performed to confirm the diagnosis. These tests involve looking at the blood and urine for substances that are abnormally elevated in MCAD deficiency including acylcarnitines, organic acids, and acylglycine. Genetic testing can also confirm a diagnosis of MCAD deficiency. These tests involve looking for changes (mutations) in the ACADM gene known to cause the disorder.

If you believe your child may have MCAD deficiency, talk to your pediatrician. He or she may refer you to a medical geneticist, metabolic dietician or genetic counselor to discuss further tes. They can help decide if testing is right for you, and can order this testing if necessary. A medical geneticists can be found by asking your doctor for a referral or looking on the American College of Medical Geneticists website. Genetic counselors can be found on the National Society of Genetic Counselors website. A metabolic dietician can be found through the Genetic Metabolic Dieticians International webpage.

References
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More Diagnosis and Testing Content

Is there newborn testing for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Is there more than one test for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Who else in my family should I test for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Can medium-chain acyl-CoA dehydrogenase (MCAD) deficiency be detected before birth?

Is there newborn testing for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Most people with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency are diagnosed after a positive result from testing done at birth called newborn screening. In the past, MCAD deficiency was not often diagnosed until a baby was very sick or after they passed away from apparent sudden infant death syndrome (SIDS). Now newborn screening for MCAD deficiency happens in all states in the United States. During routine newborn screening, a tiny sample of blood is taken from the heel of a newborn. This test called a heel prick or Guthrie test involves getting a few drops of blood from a pinprick in the newborn's heel. The blood is run through a machine that can detect high levels of a specific fat. This result is called "Elevated C8 (often also C6, C10, C10:1 and C8/C10)." Having a positive newborn screen with these high levels does not mean for sure that a baby has been diagnosed with MCAD deficiency, but doctors usually work closely with metabolic dietitians and medical geneticists as they learn more about the baby and do additional blood tests to confirm a diagnosis. These tests involve looking at the blood and urine for substances that are abnormally elevated including acylcarnitines, organic acids, and acylglycine. Genetic testing can also confirm a diagnosis. These tests involve looking for changes (mutations) in the ACADM gene known to cause the disorder.

To find a medical professional nearby who can discuss information and testing, medical geneticists can be found by asking your doctor for a referral or looking on the American College of Medical Geneticists website. Genetic counselors can be found on the National Society of Genetic Counselors website. A metabolic dietician can be found through the Genetic Metabolic Dieticians International webpage.

References
Is there more than one test for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Most infants with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency are diagnosed through routine newborn screening or NBS. NBS shows high levels of acylcarnitine in a blood sample from people with MCAD deficiency. Further testing to confirm a diagnosis will be done. This will include testing the blood and urine for substances that are abnormally elevated in people with MCAD deficiency including acylcarnitines, organic acids, and acylglycine. Sometimes, NBS can miss an infant with MCAD deficiency.

Genetic testing can be used to confirm a diagnosis of MCAD deficiency, but is often not necessary. These tests involve studying the ACADM gene for changes that cause the disorder. This can include targeted mutation analysis, where specific, known changes in a gene are looked for; single-gene testing, where the ACADM gene is studied for any changes; or, deletion/duplication analysis, where missing or extra regions of DNA are looked for within a specific gene. Molecular genetic testing must be done at specialized laboratories.

References
  • Matern D, Rinaldo P. Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency. GeneReviews website. https://www.ncbi.nlm.nih.gov/books/NBK1424/#mcad
  • Gartner V, McGuire PJ, Lee PR. Child Neurology: Medium-chain acyl-coenzyme A dehydrogenase deficiency. Neurology. 2015;85(4):e37-e40.
Who else in my family should I test for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

In a family with a person with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, tests can be done to see whether other family members are carriers for the disorder. (Carriers do not have symptoms and have one working and one non-working copy of the ACADM gene.) Doctors will run blood and urine tests on at-risk family, which include all first degree relatives. Blood and urine tests are used to detect substances that are abnormally elevated in people with MCAD deficiency including acylcarnitine, organic acids, and acylglycine.

Genetic testing can also be used to detect affected family members. However, the specific gene changes in the ACADM gene in that family need to be known to perform such testing. If the gene change is known, all siblings and other at-risk relatives can be tested. Molecular genetic testing, which are tests that look for changes in genes, can be performed.

A genetic counselor or a physician with experience in MCAD deficiency can provide advice about how a confirmed diagnosis can affect other family members. A medical geneticist can be found by asking your doctor for a referral or looking on the American College of Medical Geneticists website. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
  • Matern D, Rinaldo P. Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency. GeneReviews website. https://www.ncbi.nlm.nih.gov/books/NBK1424/#mcad
  • Gartner V, McGuire PJ, Lee PR. Child Neurology: Medium-chain acyl-coenzyme A dehydrogenase deficiency. Neurology. 2015;85(4):e37-e40.
Can medium-chain acyl-CoA dehydrogenase (MCAD) deficiency be detected before birth?

Some parents may choose to have their child tested for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency before they are born. This is known as prenatal diagnosis. If the gene change(s) that causes MCAD deficiency are known in a family, then molecular genetic testing (which can detect these changes) can be used for prenatal diagnosis. A sample of tissue can be taken from the placenta to test for changes in the ACADM gene. This test is called chorionic villus sampling. Another test is called amniocentesis, which involves taking a sample of the amniotic fluid that surrounds and protects a developing fetus. Cells known as amniocytes are taken from the fluid and studied for changes in the ACADM gene.

Making a diagnosis of MCAD deficiency before birth is also possible through an enzyme assay on placental tissue or amniocytes. An assay is a test that measures the activity of an enzyme; in this instance the activity of the MCAD enzyme.

There are risks to the unborn baby of doing these tests before birth and with disorders like MCAD deficiency, which do not affect intelligence, such testing is not commonly done. Talk to your doctor or a genetic counselor in your area to discuss the risks and benefits of prenatal diagnosis. Genetic counselors can be found on the National Society of Genetic Counselors website.

References
  • Matern D, Rinaldo P. Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency. GeneReviews website. https://www.ncbi.nlm.nih.gov/books/NBK1424/#mcad
  • Gartner V, McGuire PJ, Lee PR. Child Neurology: Medium-chain acyl-coenzyme A dehydrogenase deficiency. Neurology. 2015;85(4):e37-e40.

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