Diagnosing Maple Syrup Urine Disease

Maple Syrup Urine Disease (MSUD) is an inherited disorder that typically starts showing symptoms in infants within the first few days to the first few weeks after birth. Without proper treatment, this disease can be fatal. It is a lifelong condition that individuals have to monitor and treat throughout their lives. 

What Is Maple Syrup Urine Disease?

Maple Syrup Urine Disease results when the body is unable to break down amino acids properly. Amino acids are vital for many processes in the body but the body must also break down and remove amino acids that aren’t necessary to function. Infants suffering from MSUD are not capable of breaking down certain amino acids—specifically valine, leucine, and isoleucine. These amino acids build up in the body until they reach dangerous levels in the urine and blood. One of the identifying symptoms of this condition is the sweet-smelling urine from which the condition gets its name.

Symptoms Of Maple Syrup Urine Disease

In addition to sweet-smelling urine, other symptoms of MSUD include:

  • Lack of interest in breastfeeding
  • Poor or no appetite
  • Problems breathing
  • Weight loss
  • Vomiting
  • Lack of energy
  • Fussiness or irritability
  • Seizures
  • Coma

Maple Syrup Disease Is an Inherited Disorder

MSUD is caused by a mutated gene an infant receives from both the mother and the father. Both parents must pass on this mutated gene to an infant for it to cause the disorder. If a person has inherited the mutated gene from just one parent, they are considered a carrier and will have no adverse effects.

If you and your partner are both carriers and have a baby, there is a:

  • 25% chance that your child will have MSUD.
  • 50% chance your child will be a carrier, if they do not develop the disease itself. 

Through comprehensive carrier screening, it is possible to know if you or your partner carries the MSUD gene mutation. Whether you are currently pregnant or planning to become pregnant in the future, this screening can provide you with the information you need prior to birth. 

How Maple Syrup Urine Disease Is Diagnosed

Thankfully, most doctors test for MSUD the first week of birth. This is imperative because, if it is diagnosed, the infant must start a special diet immediately. In the US, virtually all babies are tested for it.


Breast milk contains amino acids, so breastfeeding must be closely monitored by a medical professional. Special formulas are often used to feed an infant with MSUD. 

MSUD is also treated through a specialized diet low in high-protein foods—this includes the limiting of foods such as meat, fish, eggs, and cheese. A dietician or other medical professional will help monitor the diet. 

Although there is no cure, a liver transplant can remove the need for any special diet or risk of toxic buildup. However, liver transplants are a major undertaking that is not a viable option for everyone. 

MSUD is a serious condition that affects patients around the world. With the help of comprehensive carrier screening and testing procedures in place, MSUD can be identified early so that treatment can start right away. 

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