What is Maple Syrup Urine Disease

Maple syrup urine disease is a genetic disorder that is passed down through families. The name of the disease comes from the maple syrup smell of the urine in people with this condition.

People with this condition are unable to break down three amino acids that the body needs for normal growth, development, and functioning. These amino acids include leucine, isoleucine, and valine. They come from one’s diet. Protein-rich foods like milk, meat, and eggs are high in these amino acids. Symptoms of this condition are often noticed when these amino acids build up throughout the body and become toxic.

Severe forms of maple syrup urine disease (classic type) start in early infancy. Milder forms may develop later in childhood. There is no cure for this disease, but early diagnosis and treatment with a special diet can prevent serious complications.

This diet must be started as soon as the condition is diagnosed and be continued for life. If untreated, the disorder can lead to seizures, coma, and death.

What are the causes?

This condition is caused by abnormal genes (mutations) that are passed down through families. A child needs to get the mutated gene from both parents to have the condition. A person who gets the gene from one parent will not have the condition, but could pass it on to his or her children. This person is called a carrier. If both parents are carriers, their children have a 1 in 4 chance of being born with maple syrup urine disease.

What increases the risk?

You are more likely to develop this condition if:

• You have a family history of the condition.
• You are an American Mennonite or Ashkenazi Jew.

What are the signs or symptoms?

Signs and symptoms depend on the type of maple syrup urine disease.

• Severe maple syrup urine disease starts soon after birth. Signs and symptoms in babies include:
  • Poor feeding.
  • Vomiting.
  • Failure to move and be active (lethargy).
  • Abnormal movements or stiffness.
  • Seizures.
• Symptoms of mild maple syrup urine disease in adults and children include:
  • Attention deficit hyperactivity disorder (ADHD) symptoms.
  • Depression.
  • Anxiety.
  • Learning difficulties.
  • Weak bones (osteoporosis).
  • Stomach pain, nausea, and vomiting caused by inflammation of the pancreas.
  • Headache, nausea, and vomiting caused by pressure inside the brain.
• Both adults and children may have symptoms even when they are on diet treatment. Symptoms can get severe if:
  • They stop their diet. If treatment is not given soon, seizures and coma may occur.
  • They are under stress. Stress increases protein breakdown in the body. Stress triggers may include:
    • Infection.
    • Injury.
    • Fasting.
    • Emotional stress.

How is this diagnosed?

This condition may be diagnosed:

• Before birth. A sample of amniotic fluid can be tested to see if the unborn baby has the condition. This is usually done by parents who know they carry the genetic defect or have a family history of the disorder.
• At birth. Newborns are usually screened for the condition along with other inherited disorders. A child with a mild form of the disorder may not test positive at birth.
• Later in life. A health care provider may suspect the condition based on the child’s symptoms. The child will have: 
  • A physical exam. 
  • Other tests, including:
    • Blood and urine tests to look for amino acids.
    • Genetic testing to look for defects associated with the disorder.

How is this treated?

Treatment for this condition depends on its severity and when it was diagnosed.

• If diagnosed at birth, a special formula is given to babies. This formula is free of the amino acids leucine, isoleucine, and valine.
• If diagnosed in childhood or adulthood, a special diet is created based on tests of amino acids in your blood. You will be given a diet that has enough nutrition without proteins that can become toxic.

Other treatments include:

• Taking vitamin B1 supplements (thiamine).
• A procedure (hemofiltration) that filters out amino acids and from the clear portion of the blood (plasma). This is only needed in a toxic crisis caused by stress. It must be done right away in the hospital.
• A liver transplant. This is experimental treatment, with no guarantee that the new liver will work. It may be done for those with severe disease.

Follow these instructions at home:

Eating and drinking

• Follow instructions from the health care provider and dietitian about eating or drinking restrictions. Work closely with the health care provider and dietitian to maintain a protein-restricted diet.
• Do not fast or skip meals.
• Do not make any changes to your diet without talking to a health care provider and dietitian.

General instructions

• Take over-the-counter and prescription medicines only as told by the health care provider.
• Return to normal activities as told by the health care provider. Ask a health care provider what activities are safe.
• Keep all follow-up visits as told by the health care provider. This is important.

Contact a health care provider if:

• Symptoms of maple syrup urine disease are getting worse.
• You have trouble following the restricted diet.

Get help right away if:

• You notice symptoms of maple syrup disease crisis caused by infection, stress, injury, or diet changes. These include:
  • Vomiting.
  • Lethargy.
  • Seizures.

These symptoms may represent a serious problem that is an emergency. Do not wait to see if the symptoms will go away. Get medical help right away. Call your local emergency services (911 in the U.S.). Do not drive yourself to the hospital.

Summary

• Maple syrup urine disease is a disorder that a person is born with.
• This condition is caused by genetic defects that are passed down through families.
• Severe forms of the condition start in infancy.
• There is no cure for this disease, but early diagnosis and treatment with a special diet can prevent serious complications.
• Get help right away if you notice symptoms of maple syrup disease crisis caused by infection, stress, injury, or diet changes. These symptoms may get worse quickly and lead to seizure or coma.