Maple syrup urine disease

Definition:

An inheritable metabolic disease of amino acid metabolism characterized by acidosis, central nervous system symptoms, and urine that smells like maple syrup.

Causes, incidence, and risk factors:

Maple syrup urine disease (MSUD) is caused by the inability to metabolize the amino acids leucine, isoleucine, and valine. The disease is so named 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 die in the first few weeks of life. MSUD also occurs in an intermittent form and a mild form. Even the mildest form, MSUD results in retardation and bouts of acidosis precipitated by stresses such as illness.