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. Genetic counseling is suggested for prospective parents with a family history of maple syrup urine disease. Acute acidosis is treated to restore normal pH. Peritoneal dialysis can be used to remove the high levels of amino acids . Strict compliance is necessary to prevent neurological damage.