Maple syrup urine disease Health Article

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 can smell like maple syrup.

Alternative Names

MSUD

Causes, incidence, and risk factors

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 buildup 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, repeated periods of physical stress can cause mental retardation and high levels of leucine.

Symptoms

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

Signs and tests

• Plasma amino acid test
• Urine amino acid test

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

Treatment

When the condition is diagnosed, and during episodes, treatment involves eating a protein-free diet. Fluids, sugars, and possibly fats are given through a vein (IV). Peritoneal dialysis or hemodialysis can be used to reduce the level of amino acids.

A special diet free of branched-chain amino acids is started when amino acid levels are normal. The health care provider will follow these levels closely, and will adjust the diet based on amino acid levels.

Long term treatment requires a special diet. The diet includes a man-made 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 follow this diet to prevent nervous system (neurological) damage. This requires frequent blood tests and close supervision by a registered dietitian and physician, as well as cooperation by the parents.