Conditions Medium-Chain Acyl-CoA Dehydrogenase Deficiency

Medium-chain acyl-CoA dehydrogenase deficiency (MCAD) is a condition in which the body is unable to break down certain fats. It is considered a fatty acid oxidation condition because people affected with MCAD are unable to change some of the fats they eat into energy the body needs to function. Instead, too many unused fatty acids build up in the body. If untreated, MCAD can cause brain damage and breathing problems. However, if the condition is detected early and proper treatment is begun, people affected by MCAD can often lead healthy lives.

Condition Type

Fatty Acid Oxidation Disorders


Medium-chain acyl-CoA dehydrogenase deficiency is estimated to affect one out of every 15,000 babies born in the United States. It is more common in people of northern European ancestry.

Also known as

  • MCAD
  • ACADM deficiency
  • MCADH deficiency
  • Medium-chain acyl-coenzyme A dehydrogenase deficiency

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of MCAD (see Early Signs below). If your baby has certain signs, your baby’s doctor may suggest starting immediate treatment.

If your baby’s newborn screening result for medium-chain acyl-CoA dehydrogenase deficiency (MCAD) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your baby to have additional testing. It is important to remember that an out-of-range screening result does not necessarily mean that your child has the condition. An out-of-range result may occur because the initial blood sample was too small or the test was performed too early. However, as a few babies do have the condition, it is very important that you go to your follow-up appointment for a confirmatory test. Because the harmful effects of untreated MCAD can occur soon after birth, follow-up testing must be completed as soon as possible to determine whether or not your baby has the condition.

Follow-up testing will involve checking your baby’s urine and blood samples for harmful levels of acids and toxins. Certain acids and toxins build up in the body when a child has a fatty acid oxidation condition, so measuring the levels of these substances in your baby’s body can help doctors determine if your baby has a condition. A specific pattern of acylcarnitines in the blood and other organic acids in the urine might indicate that your baby has MCAD. Sometimes follow-up testing may also include testing a very small sample of skin.

About Medium-Chain Acyl-CoA Dehydrogenase Deficiency

Early Signs

The first signs of medium-chain acyl-CoA dehydrogenase deficiency (MCAD) usually begin during infancy or early childhood (three months to three years of age). You might see signs such as:

  • Sleeping longer or more often
  • Tiredness
  • Behavior changes
  • Irritable mood
  • Poor appetite
  • Fever
  • Diarrhea
  • Low blood sugar (referred to as hypoglycemia)
  • Vomiting

Many of these signs may occur when your baby eats foods that his or her body cannot break down. They can be triggered by long periods of time without eating, illnesses, and infections.

If your baby shows any of these signs, be sure to contact your baby’s doctor immediately.


Dietary Treatment

Your baby will need to be on a restricted diet to avoid the types of fats your baby’s body cannot break down. A dietician or a nutritionist can help plan a high-carbohydrate, low-fat diet that still gives your baby the nutrients he or she needs for healthy growth.

Eating often will also help prevent your baby from experiencing many of the signs mentioned in the Early Signs section.

Supplements and Medication

Your baby’s doctor might prescribe L-carnitine supplements. L-carnitine is a substance that most individuals make naturally, but your baby’s body might not be making enough of it. Prescription L-carnitine helps your baby’s body break down fats and remove harmful substances.

Expected Outcomes

Children who receive early treatment for medium-chain acyl-CoA dehydrogenase deficiency (MCAD) have healthy growth and development.

If MCAD is not treated, children may experience breathing problems, seizures, liver troubles, brain damage, coma, and possibly death. Early screening and treatment can avoid these effects.


When we eat food, enzymes help break it down. Certain enzymes help break down fats into their building blocks, fatty acids.

Fatty acids are built like chains and come in many lengths. They are categorized as either short, medium, long, or very long. Different enzymes work on breaking down different lengths of fatty acids. An enzyme called medium-chain acyl-CoA dehydrogenase is in charge of breaking down medium-length fatty acids. If you have a question about what makes a fatty acid “medium” length, read about it here.

If your baby has medium-chain acyl-CoA dehydrogenase deficiency (MCAD), your baby’s body either does not make enough or makes non-working medium-chain acyl-CoA dehydrogenase enzymes. When this happens, your baby cannot use medium-length fatty acids for energy. This is harmful because your baby’s body needs fat for energy when his or her body runs out of sugars (such as between meals). The heart also needs fatty acids for energy.

MCAD is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for MCAD, one from each parent, in order to have the condition. The parents of a child with an autosomal recessive condition each carry one copy of the non-working gene, but they typically do not show signs and symptoms of the condition. While having a child with MCAD is rare, when both parents are carriers, they can have more than one child with the condition. Learn more about autosomal recessive inheritance.

Support for Medium-Chain Acyl-CoA Dehydrogenase Deficiency

Support Services

Support groups can help connect people who have a child or other family member affected with medium-chain acyl-CoA dehydrogenase deficiency (MCAD) with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for affected individuals and their families, as well as health care providers.

The New England Regional Genetics Network created a website called "GEMSS: Genetics Education Materials for School Success." When your child reaches school age, you can provide teachers and school administration with this resource specifically for children with MCAD.

Accessing Care

Work with your baby’s doctor to determine the next steps for your baby’s care. Your baby’s doctor may help you coordinate care with a physician who specializes in metabolism, a dietician who can help plan your child’s specialized diet, and other medical resources in your community. Some children who experience severe symptoms from untreated medium-chain acyl-CoA dehydrogenase deficiency (MCAD) may have developmental delays. If you think that your baby is not meeting his or her developmental milestones, ask your baby’s doctor about the next steps in accessing a developmental evaluation and care.

Because MCAD is a genetic condition, you may want to talk with a genetics specialist. A genetic counselor or geneticist can help you understand the causes of the condition, discuss genetic testing for MCAD, and understand what this diagnosis means for other family members and future pregnancies. Speak with your baby’s doctor about getting a referral. The Clinic Services Search Engine offered by the American College of Medical Genetics and Genomics (ACMG) and the Find a Genetic Counselor tool on the National Society of Genetic Counselors (NSGC) website are two good resources for you or your baby's health care provider to use to identify local specialists.

Families' Experiences

Alex was diagnosed with medium-chain acyl-CoA dehydrogenase deficiency (MCAD) through newborn screening. Read his story and the stories of other families affected by MCAD on the Save Babies through Screening Foundation website.

The FOD Family Support group publishes the stories of families who have a child with MCAD. Read the stories here.

References & Sources

Visit MedlinePlus Genetics for more condition information

Visit the Screening, Technology And Research in Genetics (STAR-G) Project for more information on MCAD

ACT Sheets

Healthcare professionals can learn more about confirmatory testing by reading the American College of Medical Genetics and Genomics' Algorithm for Diagnosis and ACT Sheet, a guide for follow-up after newborn screening. You can visit this page of the ACMG website here.

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