Acyl-coa dehydrogenase, medium-chain, deficiency of


What is medium-chain acyl-CoA dehydrogenase (MCAD) deficiency?

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a genetic condition that prevents a person's body from being able to break down a specific type of body fat to make energy. Most of the time, the body uses available fuels such as sugars to make energy. However, if a person is sick and not eating (fasting), dieting, or stressed, they may not be eating a normal amount of food to provide the body with those sugars. In these times, the body uses other sources of fuel such as fatty acids. A person with MCAD deficiency cannot break down these fatty acids and this causes medical problems during illness or fasting. This is called a metabolic crisis or metabolic decompensation. These problems may include problems eating, nausea, vomiting, diarrhea, a lack of energy (lethargy) or infants or children being very sleepy, low blood sugar (hypoglycemia), and liver problems. Without treatment, these medical issues can quickly turn serious and lead to heart problems, breathing difficulties, coma, or even sudden death. To be as healthy as possible, people with MCAD deficiency need to avoid going long periods of time without eating. They should also have an emergency plan if they become ill or are unable to eat. If diagnosed and started on an appropriate therapy, people with MCAD deficiency can often lead healthy lives with a normal life expectancy.

People with MCAD deficiency may experience their first symptoms when they are a baby or young child. 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 testing at birth (newborn screening) happens in all states in the United States. A newborn screen that suggests a baby may have MCAD deficiency is one with 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.

To find a metabolic dietitian specializing in diets for people with metabolic conditions like MCAD deficiency, visit the GMDI Find a Metabolic Dietitian webpage.

To find a medical professional nearby who can discuss information and testing, 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.

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Are there other names for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

How common is medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Are there different forms of medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Are there other names for medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Sometimes, there are different names for the same disorder. There are a few different ways doctors may refer to medium-chain acyl-CoA dehydrogenase (MCAD) deficiency including:

  • ACADM deficiency
  • MCAD deficiency
  • MCADH deficiency
  • Medium chain acyl-CoA dehydrogenase deficiency
  • Medium-chain acyl-coenzyme A dehydrogenase deficiency
How common is medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a rare disorder. Rare disorders often go unrecognized or misdiagnosed and the incidence and prevalence of individual rare disorders is often unclear or unknown. Prevalence is the measurement of all individuals affected by the disease at a particular time. Incidence is the number of new people with a disorder or newly-diagnosed. One estimate places the incidence at one in 17,000 live births in the United States. Based on the results of newborn screening in certain states the incidence ranges from one in 13,000-19,000 live births. MCAD deficiency is more common in people of northeastern European ancestry.

Are there different forms of medium-chain acyl-CoA dehydrogenase deficiency (MCAD)?

As the use of newborn screening has expanded, infants have been identified that have milder forms of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. Many of these individuals may never have an episode of metabolic crisis because they have higher levels of the MCAD enzyme than people with the more severe forms of MCAD deficiency. However, some doctors feel that these people are at risk under certain circumstances of having a metabolic episode, and there are times when people have symptoms of MCAD deficiency for the first time as adults. People with the "mild" forms of MCAD deficiency should receive the same counseling and precautions as people with the severe forms.

  • Dessein AF, Fontaine M, Andresen BS, et al. A novel mutation of the ACADM gene (c.145C>G) associated with the common c.985A>G mutation on the other ACADM allele causes mild MCAD deficiency: a case report. Orphanet J Rare Dis. 2010;5:26.
  • Matern D, Rinaldo P. Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency. GeneReviews website.

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