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Methylmalonic acidemia (methylmalonyl-CoA mutase)

(meth-uhl-muh-LAHN-IK • a-suh-DEE-mee-uh (meth-uhl-muh-LAHN-uhl • koh-AY • MYOO-tace))

General Condition Information

Other Names

  • Methylmalonic acidemia
  • Methylmalonic acidemia (methylmalonyl-CoA mutase deficiency)
  • Methylmalonic acidemia (mutase deficiency form)
  • Methylmalonic acidemia (mutase deficiency)
  • Methylmalonic acidemia due to mutase deficiency
  • Methylmalonic acidemia methylmalonyl-CoA mutase
  • Methylmalonic acidemia mutase
  • Methylmalonic acidemia mutase deficiency
  • Methylmalonic acidemia – mutase deficiency
  • Methylmalonic acidemia, methylmalonyl-CoA mutase
  • Methylmalonic acidemia, mutase deficiency form
  • Methylmalonic acidemia- methylmalonyl- CoA mutase
  • Methylmalonic acidemia- mutase deficiency
  • Methylmalonic acidemia: Methylmalonyl-CoA mutase deficiency
  • Methylmalonic acidemia: mutase deficiency
  • Methylmalonic acidemias
  • Methylmalonyl-CoA mutase deficiency

Condition Type

Birth Prevalence

  • This condition is one type of a group of conditions known as methylmalonic acidemias. It is estimated that fewer than 80 babies are born with methylmalonic acidemias each year in the United States.
  • Visit GeneReviews to learn more about how often this condition occurs.

Screening Finding

Increased C3 acylcarnitine (also known as propionyl carnitine) +/- increased methylmalonic and methylcitric acid

What is methylmalonic acidemia (methylmalonyl-coa mutase)

There are different forms of methylmalonic acidemia, each with different causes and treatments. Methylmalonic acidemias are inherited (genetic) conditions that prevent the body from breaking down certain proteins, cholesterol, and fats. 

Methylmalonic acidemias happen when an enzyme called methylmalonyl CoA mutase (mut) does not work correctly. This enzyme uses vitamin B-12 to help digest certain proteins, fats, and cholesterol to use them or get rid of them.

Methylmalonic acidemia (methylmalonyl-CoA mutase) is a type of methylmalonic acidemia where this enzyme is not made by the body correctly. To learn about another type of methylmalonic acidemia, visit the Methylmalonic Acidemia (Cobalamin Disorders) page.

Without enough working methylmalonyl CoA mutase, your baby will have trouble making energy and getting rid of waste. This condition can be more or less severe depending on how well this enzyme works. If the baby cannot make any enzyme, the condition is called mut0, which is the most severe form. The condition is called mut- when the baby can make some enzyme that works.

If your baby’s body cannot break down proteins, lipids, and cholesterol, toxins can build up. When these toxins are acids, blood can become acidic (acidemia). Acidemia can damage your baby’s body and lead to the signs and symptoms of the condition.

Newborn Screening and Follow-Up

Condition Details

Treatment and Management

It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.

Treatments may include the following:

  • Diet low in certain proteins and fats
  • Special formulas and foods
  • Regular and frequent meals and snacks
  • Vitamin B-12 supplements (only for certain types of methylmalonic acidemia), usually given by a shot (injection) rather than by mouth
  • Carnitine supplements in some cases

Children who receive early and ongoing treatment for methylmalonic acidemia can have healthy growth and development. Even with treatment, some children may still have developmental delays or learning difficulties.

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