Maple Syrup Urine Disease



What is maple syrup urine disease?

Maple syrup urine disease (MSUD) is an inherited disorder in which the body is unable to process certain protein building blocks (amino acids) properly. Normally, our bodies break down protein foods such as meat and fish into amino acids. Any amino acids that are not needed are usually broken down and removed from the body. Babies with MSUD are unable to break down the amino acids leucine, isoleucine and valine. Very high levels of these amino acids are harmful.

One of the characteristic symptoms of MSUD is sweet-smelling urine, which gives the condition its name.

How common is maple syrup urine disease?

MSUD is a rare condition. It affects males and females in equal numbers. Estimated incidence is 1 in 185,000 live births.  Please discuss with your doctor for further information.


What are the symptoms of maple syrup urine disease?

The common symptoms of maple syrup urine disease  are:

  • Sweet-smelling urine and sweat
  • Poor feeding or loss of appetite
  • Weight loss

Babies with MSUD may also have episodes known as a “metabolic crisis”, sometimes early in their life. Symptoms of a metabolic crisis include:

  • Lack of energy
  • Vomiting
  • Irritability
  • Breathing difficulties

There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.

When should I see my doctor?

It’s important to get medical help immediately if your baby develops symptoms of a metabolic crisis.

If your baby has any signs or symptoms listed above or have any questions, please consult with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.


What causes maple syrup urine disease?

Mutations in the BCKDHA, BCKDHB, and DBT genes can cause maple syrup urine disease. These three genes provide instructions for making proteins that work together as part of a complex. The protein complex is essential for breaking down the amino acids leucine, isoleucine, and valine, which are present in many kinds of food, particularly protein-rich foods such as milk, meat, and eggs.

Mutations in any of these three genes reduce or eliminate the function of the protein complex, preventing the normal breakdown of leucine, isoleucine, and valine. As a result, these amino acids and their byproducts build up in the body. Because high levels of these substances are toxic to the brain and other organs, their accumulation leads to the serious health problems associated with maple syrup urine disease.

Researchers are studying other genes related to the same protein complex that may also be associated with maple syrup urine disease.

Risk factors

What increases my risk for maple syrup urine disease?

There are many risk factors for maple syrup urine disease , such as:

  • Genetics

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is maple syrup urine disease diagnosed?

Many infants with MSUD are identified through newborn screening programs. Tandem mass spectrometry, an advanced newborn screening test that screens for more than 30 different disorders through one blood sample, has aided in the diagnosis of MSUD. Infants with mild or intermittent forms of the disorder may have totally normal blood amino acids after birth and thus can be missed by newborn screening.

In places where testing for MSUD is unavailable or where newborn screening fails to detect MSUD, a diagnosis may be suspected based upon symptomatic findings (lethargy, failure to thrive, neurologic signs or, during a metabolic crisis, odor of maple syrup in earwax, sweat or urine). Tests to diagnose MSUD may include urine analysis to detect high levels of keto acids (ketoaciduria) and blood analysis to detect abnormally high levels of amino acids.

An enzymatic diagnosis may be confirmed through analysis of white blood cells (lymphocytes) or cells taken from an affected individual’s skin. Early diagnosis, especially in suspected individuals, allows for management of asymptomatic infants before the onset of the usual clinical manifestations. Diagnosis through DNA testing is readily available and prenatal diagnosis is available.

Molecular genetic testing for mutations in the BCKDHA, BCKDHB and DBT genes is also available to confirm the diagnosis, and is necessary for purposes of carrier testing for at-risk relatives and prenatal diagnosis for at-risk pregnancies.

How is maple syrup urine disease treated?

The treatment of classic, intermediate, intermittent, and thiamine-responsive MSUD has two chief components: lifelong therapy to maintain acceptable amino acid levels in the body and immediate medical intervention for metabolic crises.

Individuals with MSUD must remain on a protein-restrictive diet that limits the amount of branched-chain amino acids they take in. Protein-restriction must start as soon as possible after birth to promote proper growth and development.

Lifestyle changes & home remedies

What are some lifestyle changes or home remedies that can help me manage maple syrup urine disease?

The following lifestyles and home remedies might help you cope with maple syrup urine disease:

  • High-protein foods need to be limited, includingmeat, fish, cheese, eggs, pulses, and nuts. Your dietitian will provide detailed advice and guidance, as your baby still needs some of these foods for healthy growth and development.
  • Some children need to take supplements of isoleucine and valine alongside the prescribed diet. This helps to maintain a healthy level of these amino acids in the blood without causing harm. Blood tests are needed to monitor these levels.
  • Breastfeeding and baby milk also need to be monitored and measured, as advised by your dietitian. Regular baby milk contains the amino acids that need to be restricted, so a special formula is used instead. This contains all the vitamins, minerals and other amino acids your baby needs.
  • People with MSUD need to follow a low-protein diet for the rest of their life to reduce the risk of a metabolic crisis. As your child gets older, they’ll eventually need to learn how to control their diet and will stay in contact with a dietitian for advice and monitoring.

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Review Date: February 18, 2019 | Last Modified: February 18, 2019

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