MCAD deficiency is a genetic condition when your body can't convert certain fats into energy. Symptoms trigger after long periods of time when you go without eating (fasting). Symptoms include feeling tired, nauseated and having low blood sugar. Treatment includes frequent meals and a diet full of complex carbohydrates.
Medium-chain acyl-coenzyme A (acyl-CoA) dehydrogenase (MCAD) deficiency is a condition that prevents your body from turning fats into energy. This condition is most prevalent when you fast or don’t eat food for long periods of time.
In your body, there are enzymes that process food. There is a specific enzyme (medium-chain acyl-CoA dehydrogenase) that targets a group of fat called medium-chain fatty acids to convert it into a substance that your body can use (metabolize) as energy. People who have MCAD deficiency don't have enough of this enzyme and are unable to metabolize medium-chain fatty acids.
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MCAD deficiency affects people who receive a mutated copy of the ACADM gene from their parents. MCAD deficiency is a genetic condition that you inherit when both of your parents carry a copy of the mutated ACADM gene, and you inherit the mutated copy from each of your parents (autosomal recessive). Parents who carry a mutated gene have a risk of passing the gene onto their children. If both parents are carriers, the risk of passing the genetic condition onto their child is 25%. There is a 50% chance that their child will not have the condition but be a carrier, similar to their parents. There is also a 25% chance that their child won’t receive any mutated genes and won’t be a carrier.
There's nothing parents can do to prevent genetic mutations from passing to their children before or during pregnancy.
MCAD deficiency occurs in about 1 out of every 15,000 individuals. MCAD deficiency is most common among people with northern European ancestry.
MCAD deficiency affects your baby’s ability to turn fat into a source of energy. If your baby's needs for energy aren't met by the amount of energy it can create, especially during an illness or when they're unable to eat, it can make your baby feel sick, nauseated and tired.
Symptoms of MCAD deficiency normally appear during early infancy and childhood and can be triggered during an illness when your child loses their appetite or undergoes long periods of time without eating. Symptoms of MCAD deficiency include:
Serious side effects of MCAD deficiency include:
A genetic mutation of the ACADM gene causes MCAD deficiency. The ACADM gene tells your body to make medium-chain acyl-CoA dehydrogenase, which is an enzyme responsible for breaking down medium-chain fatty acids. These fatty acids are found in food and later reside in your tissues. Fatty acids are responsible for providing energy to vital organs in your body like your heart and liver, along with muscles and other tissues.
Genetic mutations happen randomly and can’t be prevented. The genetic mutation of ACADM causes your body to produce fewer enzymes that break down medium-chain fatty acids. As a result, your body is unable to produce the required amount of energy needed to stop symptoms from occurring.
People acquire MCAD deficiency through an autosomal recessive pattern, which means that your parents (carriers) both passed a mutated gene onto you. Since both parents have one mutated gene and one non-mutated gene, they don't show symptoms of the condition. Autosomal recessive conditions don't affect every generation and can appear randomly throughout your family history.
There's nothing parents can do to prevent the gene mutation from showing up before or during pregnancy.
Newborn screenings identify conditions that will affect your child’s overall health. MCAD deficiency is a condition your healthcare provider will test for during a newborn screening, which means a diagnosis is possible before your baby shows any symptoms of the condition. Your healthcare provider might order additional tests, including genetic testing, where they will take a small sample of your baby’s blood, urine or tissue to verify the diagnosis. Your healthcare provider might also recommend genetic testing of your baby’s birth parents to identify the presence of the mutated ACADM gene.
Treatment for MCAD deficiency focuses on meeting nutritional requirements for your child’s body and reducing long periods of time between meals, which may trigger symptoms of the condition. Dietary requirements for MCAD deficiency include:
For adults with MCAD deficiency, excessive alcohol consumption may cause severe symptoms (metabolic crisis). If this occurs, taking a glucose supplement or eating foods high in sugar helps manage the side effects of the condition.
Symptoms of MCAD deficiency vary based on the severity of the diagnosis. Symptoms arise during long periods without eating. Scheduling meals more frequently throughout the day helps minimize symptoms of the condition. Eating complex carbohydrates like whole grains, some types of vegetables and beans before bedtime alleviates the need to wake up in the middle of the night to maintain steady glucose levels.
Your healthcare provider might recommend meeting with a dietitian to monitor your child’s diet and exercise and to advise on healthy eating habits to alleviate symptoms of the condition.
There's no way to prevent MCAD deficiency because it's a genetic condition that passes from parents to children. To understand your risk of passing a genetic condition onto your child, visit your healthcare provider for genetic testing before you plan on becoming pregnant.
Early diagnosis and treatment of MCAD deficiency significantly improve your baby’s quality of life, and offer a good prognosis. The majority of people diagnosed with MCAD deficiency live normal and healthy lives.
An estimated 20% to 25% of babies who don't receive an MCAD deficiency diagnosis after a newborn screening may experience long-term disability or early death if they don’t receive proper treatment.
If your child needs surgery where they'll undergo anesthesia, or if they have another health-related concern where fasting is necessary to complete a procedure, your healthcare provider may admit your child into the hospital before the procedure to monitor their symptoms during a period of fasting. Your healthcare provider will set up an IV to give your child nutrients that are high in sugar (glucose-containing maintenance fluids).
If your child isn't eating well or is sick or vomiting, your healthcare provider may recommend they consume energy drinks.
The best way to take care of your child with MCAD deficiency is to minimize long periods when they go without eating by scheduling meals closer together and more frequently. Make sure your child eats a well-balanced diet with meals and snacks full of complex carbohydrates, which reduces the likelihood of symptoms arising from the condition.
You should see your healthcare provider if:
You should visit the emergency room (ER) immediately if your child diagnosed with MCAD deficiency has a seizure. Seizures are a severe side effect of the condition and cause your child to lose consciousness temporarily, move their arms and legs uncontrollably or show signs of confusion, anxiety or fear without a visible cause. Seizures normally last between 30 seconds and two minutes. Any seizure lasting more than five minutes is a medical emergency, so call 911 immediately.
Hyperammonemia is a condition where an individual has higher than normal levels of ammonia in their body. Hyperammonemia can occur after an MCAD diagnosis since they both affect your body’s metabolism (metabolic condition). Your body produces ammonia in your colon and small intestine, which transports it to your liver and then converts it into a compound that excretes from your kidneys (urea). If you have liver damage as a result of MCAD deficiency complications, your ammonia level may rise since your liver can't metabolize it. Treatment for hyperammonemia includes lifestyle changes like removing or adding certain foods to your diet. Treatment for severe hyperammonemia could include IV solutions or dialysis.
A note from Cleveland Clinic
People diagnosed with MCAD deficiency can live normal and healthy lives when accompanied by diet and lifestyle changes to avoid symptoms. Since MCAD deficiency is a genetic condition that passes from parents to children, if you plan on becoming pregnant, talk with your healthcare provider about genetic testing to understand the risks of passing the condition onto your child.
Last reviewed by a Cleveland Clinic medical professional on 10/27/2021.
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