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Maple syrup urine disease

Maple • syrup • urine • disease

General Condition Information

Other Names

  • Maple syrup disease
  • Maple syrup urine disease (Branched-chain ketoacid dehydrogenase deficiency)
  • Maple syrup urine disease (type IA, IB, II)
  • Maple syrup urine disorder

Condition Type

Birth Prevalence

  • It is estimated that fewer than 30 babies are born with this condition each year in the United States. 
  • Visit GeneReviews to learn more about how often this condition occurs.

Screening Finding

Increased leucine, isoleucine, and/or other branched-chain amino acids

What is maple syrup urine disease

Maple syrup urine disease is an inherited (genetic) condition that prevents the body from processing proteins correctly. Your body breaks down the protein you eat into parts called amino acids. Your body then uses those amino acids to make other proteins that it needs to function.

Certain enzymes break down a specific type of amino acid called branched-chain amino acids. The branched-chain amino acids are called leucine, isoleucine, and valine. 

These enzymes do not work properly in babies with maple syrup urine disease. Either the body does not make enough enzyme or does not produce the enzyme correctly. As a result, babies with maple syrup urine disease have trouble breaking down branched-chain amino acids. Leucine, isoleucine, valine, and other related substances then build up in their body and can be toxic.

There are different types of maple syrup urine disease: classic, intermediate, intermittent, thiamine-response, and unclassified. The form your baby has depends on how well these enzymes work in their body. All forms of this condition can result in sweet-smelling earwax and urine, which is how the condition got its name. The substances the body cannot remove cause this sweet smell.

Without treatment, toxic levels of branched-chain amino acids and their related substances can lead to the signs and symptoms of the condition. In severe cases, this condition can lead to coma or death if not diagnosed and treated early.

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 protein
  • Special formulas and low protein foods
  • Thiamine supplements in some cases

Children who receive early and ongoing treatment for maple syrup urine disease can have healthy growth and development. Some children may still have some symptoms and signs even with early diagnosis and treatment.

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