Conditions Malonic Acidemia

Malonic acidemia (MAL) is an inherited condition in which the body is unable to break down certain proteins. It is classified as an organic acid condition because MAL can lead to harmful levels of organic acids and toxins in the body. Signs and symptoms of the condition vary. However, early identification and treatment can improve the health of children with MAL.

Condition Type

Organic Acid Conditions


Malonic acidemia (MAL) is a rare condition. The exact number of children affected by MAL is currently unknown. Fewer than 30 cases have been reported.

Also known as

  • MAL
  • Malonyl-CoA decarboxylase deficiency
  • Malonic aciduria
  • Malonyl-coenzyme A decarboxylase deficiency
  • MCD deficiency

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of MAL (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 malonic acidemia (MAL) 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 MAL 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 an organic acid condition, so studying the levels of these substances in your baby’s body can help doctors determine if your baby has a condition. High levels of C3-D3 acylcarnitine in the blood and malonic acid in the urine might be signs that your baby has malonic acidemia. In some cases, follow-up testing may include testing a very small sample of skin.

About Malonic Acidemia

Early Signs

There are very few reported cases of malonic acidemia (MAL). According to these reported cases, signs can start any time: from just a few days after birth to 13 years of age. Usually, if your baby does not receive preventative treatment, signs of MAL will start in early childhood.

These signs include:

  • Developmental delays
  • Weak muscle tone (called hypotonia)
  • Diarrhea
  • Vomiting
  • Seizures

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 Treatments

Your baby may need a restricted diet to avoid high-fat foods. A dietician or nutritionist can help you plan the right diet to keep your baby healthy while still giving him or her the nutrients needed for growth and development.

Eating often will also help prevent your baby from experiencing many of the signs mentioned in the Early Signs section. Illnesses and infections can also trigger these signs.

Supplements and Medications

Your doctor might prescribe L-carnitine supplements to help break down fats and to remove harmful substances from the body. L-carnitine is a natural substance, but your baby’s body might not make enough of it. You will need to get a prescription from your baby’s doctor for these supplements.

Expected Outcomes

Because malonic acidemia (MAL) is rare, the outcomes are not well known.

MAL can cause an enlarged, weak heart (also called cardiomyopathy), so you may need to work with a cardiologist to monitor your child’s heart.

The dietary and supplement treatments mentioned in the Treatment section are likely to help children live much longer, but there has been no research conducted on children with MAL who receive treatments.

Without treatment, children could die during infancy.


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 for energy. In malonic acidemia (MAL) the enzyme malonyl-CoA decarboxylase is not working correctly. This enzyme’s job is to help break down fatty acids for energy.

If your baby has MAL, their body does not make enough or makes non-working malonyl-CoA decarboxylase enzymes. When this enzyme does not work correctly, your baby’s body cannot break down fatty acids for energy. If fatty acids cannot be broken down, it causes heart trouble (the heart needs fatty acids for energy) and a build-up of harmful substances in the body.

MAL is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for MAL, 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 MAL 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 Malonic Acidemia

Support Services

Support groups can help connect families who have a child or other family member affected with malonic acidemia with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for families, affected individuals, health care providers, and advocates.

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, or other medical resources in your community. Some children with malonic acidemia (MAL) 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 MAL 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 MAL, 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 do not have any family stories for this particular condition. If your family is affected by malonic acidemia, and you would like to share your story, please contact us so other families may benefit from your experience.

Each family has a unique experience and each condition is very different. However, you may find it useful to read the stories of families affected by other organic acid conditions, as some of the evaluation and treatment may be similar. You can read stories of families affected by organic acid conditions at the Organic Acidemia Association’s website.

References & Sources

Visit MedlinePlus Genetics for more condition information

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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