MSUD

Alternative names

Maple syrup urine disease

Definition

Maple syrup urine disease is an inherited disease of amino acid metabolism that causes acidosis, central nervous system symptoms, and urine that may smell sweet like maple syrup.

Causes, incidence, and risk factors

Maple syrup urine disease (MSUD) is caused by the inability to metabolize the branched-chain amino acids leucine, isoleucine, and valine. The disease is called MSUD because urine from affected people smells like maple syrup.

In the most severe form, MSUD causes severe acidosis during the first week of life. This is characterized by progressively poorer feeding, Vomiting, seizures, Lethargy, and finally coma.

Untreated infants may die in the first few weeks of life in severe forms of the disease. MSUD also occurs in an intermittent form and a mild form. Even in the mildest form, infections can cause mental retardation and bouts of acidosis.

Symptoms

• Family history of MSUD or unexplained infant death
  
• Urine which smells like maple syrup
  
• Feeding difficulties
  
• Lethargy
  
• Vomiting
  
• Seizures
  
• Coma
  
• Avoiding food
  

Signs and tests

• Urine amino acids (elevated levels of the amino acids leucine, isoleucine, and valine)
  
• Plasma amino acids (elevated levels of leucine, isoleucine, and valine)
  
• Ketosis (elevated levels of ketone bodies in urine and plasma)
  
• Acidosis (excess acid in blood)
  

Treatment
Treatment of the acute episode:

• Acute acidosis is treated to restore normal pH.
  
• Because this is a protein intolerance disease, protein is cut from the diet .
  
• High doses of intravenous fluid, sugar and fat are given to prevent dehydration and provide energy to stimulate protein synthesis, which lowers the levels of the amino acids which cannot be broken down.
  
• Peritoneal dialysis or are used to remove the high levels of amino acids.