Maple syrup urine disease

Definition

Maple syrup urine disease (MSUD) is a metabolism disorder passed down through families in which the body cannot break down certain parts of proteins. Urine in persons with this condition smells like maple syrup.

Alternative Names

Causes

Maple syrup urine disease (MSUD) is caused by a gene defect. Persons with this condition cannot break down the branched-chain amino acids leucine, isoleucine, and valine. This leads to a build-up of these chemicals in the blood.

In the most severe form, MSUD can damage the brain during times of physical stress (such as infection, fever, or not eating for a long time).

MSUD also occurs in an intermittent form and a mild form. Even in the mildest form, infections can cause mental retardation and high levels of leucine.

Symptoms

• Avoiding food
• Coma
• Feeding difficulties
• Lethargy
• Seizures
• Urine that smells like maple syrup
• Vomiting

Exams and Tests

• Urine amino acid test
• Plasma amino acid test

There will be signs of ketosis and acidosis (excess acid in blood).

Treatment

Treatment involves a protein-free diet. During a flare up, fluids, sugars, and fats are given by IV. Peritoneal dialysis or hemodialysis are used to reduce the level of amino acids.

A special diet free of branched-chain amino acids is started immediately.

Long term treatment requires a special diet. The diet includes a synthetic infant formula with low levels of the amino acids leucine, isoleucine, and valine. Persons with this condition must remain on this diet permanently. It is very important to always stick to this diet to prevent neurological damage. This requires frequent blood tests and close supervision by a registered dietitian and a physician, as well as parental cooperation.

Outlook (Prognosis)

This disease can be life threatening if untreated.

Even with dietary treatment, stressful situations and illness can still cause high levels of certain amino acids. Death may occur during these episodes. With strict dietary treatment, children have grown into healthy adulthood.

Possible Complications

• Coma
• Death
• Neurological damage

When to Contact a Medical Professional

Call your health care provider if you have a family history of MSUD and are planning to start a family. Also call immediately if you have a newborn who exhibits symptoms suggestive of maple syrup urine disease.

Prevention

Genetic counseling is suggested for prospective parents with a family history of maple syrup urine disease. Some states, such as Pennsylvania, screen all newborns for signs of MSUD.

If a screening test shows that your baby may have MSUD, a follow-up blood test for amino acid levels should be done right away to confirm the disease.