Conditions Medium/Short-Chain L-3 Hydroxyacyl-CoA Dehydrogenase Deficiency

Medium/short-chain acyl-CoA dehydrogenase deficiency (M/SCHAD) is a condition in which the body is unable to break down certain fats. M/SCHAD is considered a fatty acid oxidation condition because people affected with the condition are unable to change some of the fats they eat into energy the body needs to function. This can cause unused fatty acids to build up in the body. Most individuals who are identified as having M/SCHAD never experience symptoms, but some individuals experience serious health effects from M/SCHAD.

Condition Type

Fatty Acid Oxidation Disorders


Medium/short-chain acyl-CoA dehydrogenase deficiency (M/SCHAD) is a very rare condition. The exact number of people affected with M/SCHAD is unknown.

Also known as

  • 3 hydroxyacyl-CoA dehydrogenase deficiency
  • 3-alpha-hydroxyacyl-coenzyme A dehydrogenase deficiency
  • HAD deficiency
  • HADH deficiency
  • HADHSC deficiency
  • 3-hydroxyacyl-coenzyme A dehydrogenase deficiency
  • M/SCHAD deficiency
  • SCHAD deficiency
  • Medium/short-chain hydroxyacyl-CoA dehydrogenase deficiency

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of M/SCHAD (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/short-chain acyl-CoA dehydrogenase deficiency (M/SCHAD) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your child 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 M/SCHAD 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 amounts 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 amounts of these substances in your baby’s body can help doctors determine if your baby has a condition. High levels of C4-hydrocy acylcarnitine in the blood and hydroxyl-dicarboxylic acids in the urine might indicate that your baby has M/SCHAD. Sometimes follow-up testing may also include testing a very small sample of skin.

About Medium/Short-Chain L-3 Hydroxyacyl-CoA Dehydrogenase Deficiency

Early Signs

Signs of medium/short-chain L-3 hydroxyacyl-CoA dehydrogenase deficiency (M/SCHAD) usually begin during infancy or early childhood. These signs are highly variable from person to person. Your baby may have many of them or none at all.

Signs of M/SCHAD include:

  • Sleeping longer or more often
  • Behavior changes
  • Irritability
  • Poor appetite
  • Fever
  • Diarrhea
  • Vomiting
  • Low blood sugar (called hypoglycemia)
  • Trouble breathing
  • Weak muscle tone (known as hypotonia)
  • Seizures (Epilepsy)

Many of these signs may occur when your baby eats foods that their 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 may need to be on a restricted diet in order to avoid foods that contain fats their body cannot break down. A dietician or nutritionist can help you plan a healthy diet for your baby.

Eating often can also help your baby avoid many of the signs mentioned in the Early Signs section.

<pSupplements and Medications

Some children with medium/short-chain L-3 hydroxyacyl-CoA dehydrogenase deficiency (M/SCHAD) take prescription L-carnitine supplements. L-carnitine is a substance naturally made by the body, but your baby’s body might not make enough. Taking L-carnitine supplements can help the body break down fat for energy and remove harmful substances. Your baby’s doctor will need to write a prescription for these supplements.

M/SCHAD can cause dangerously high insulin levels in some children. If your baby has levels of insulin that are too high, your baby’s doctor may prescribe medications to help your baby’s body regulate insulin levels.

Expected Outcomes

If medium/short-chain L-3-hydroxyacyl-CoA dehydrogenase (M/SCHAD) is treated early, children may have healthy growth and development. This is why newborn screening is so important.

We do not yet know how effective the treatments for M/SCHAD are. Children may still be at risk for some signs of the condition, such as high blood sugar, high insulin levels, enlarged heart, an irregular heartbeat, or liver trouble.

Babies who do not receive treatment for M/SCHAD are at risk of life-threatening heart and breathing problems, brain damage, or coma.


When we eat food, enzymes help break it down. Some enzymes help break down fats into their building blocks, called fatty acids. Other enzymes break down these fatty acids.

Fatty acids are built like chains, and they come in a variety of lengths. They are classified as either short, medium, long, or very long. Different enzymes help break down different lengths of fatty acid chains. The enzyme 3-hydroxyacyl-CoA dehydrogenase is one enzyme that breaks down medium and short-chain fatty acids for energy. If you have a question about what makes a “short” or “medium” fatty acid, read about it here.

In medium/short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency (M/SCHAD), the enzyme 3-hydroxyacyl-CoA dehydrogenase is not working correctly. If your baby has M/SCHAD, their body makes non-working or does not make enough 3-hydroxyacyl-CoA dehydrogenase. When this happens, your baby’s body cannot break down medium and short chain fatty acids for energy.

Fatty acids are important sources of energy for the heart, especially when sugar is low (such as between meals). When fatty acids cannot be broken down, harmful substances can build up in the body.

M/SCHAD is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for M/SCHAD, 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 M/SCHAD 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/Short-Chain L-3 Hydroxyacyl-CoA Dehydrogenase Deficiency

Support Services

Support groups can help connect families who have a child or other family member affected with medium/short-chain acyl-CoA dehydrogenase deficiency 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 for health care providers:

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 with medium/short-chain acyl-CoA dehydrogenase deficiency (M/SCHAD) have developmental delays. If you think that your baby is not meeting their developmental milestones, ask your baby’s doctor about the next steps in accessing a developmental evaluation and care.

Because M/SCHAD 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 M/SCHAD, 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

At this time we have not located a family story for this particular condition. If your family is affected by medium/short-chain acyl-CoA dehydrogenase deficiency (M/SCHAD) and you would like to share your story, please contact us so other families may benefit from your experience.

Each family's experience with a condition is unique, but there are some parts of the evaluation and treatment of M/SCHAD that are similar to other fatty acid oxidation conditions. You may find it useful to read the stories of families affected by other fatty acid oxidation conditions on the family story page of the FOD Family Support Group website.

References & Sources

Visit MedlinePlus Genetics for more condition information

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

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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