Maple Syrup Urine Disease (MSUD)



Maple syrup urine disease (MSUD) is a condition in which the body is unable to break down certain proteins. The condition is named for the sweet odor of the urine of untreated babies. Individuals with MSUD have trouble breaking down certain amino acids, the building blocks of proteins. Early detection and treatment can often prevent many of the serious outcomes of MSUD. Forms of MSUD vary widely in the severity of  signs. “Classic MSUD” is the most common form and is seen in babies. Babies with classic MSUD usually begin showing signs shortly after birth. These signs include poor appetite, trouble sucking during feeding, weight loss, high pitched cry, urine that smells sweet like maple syrup or burnt sugar, sleeping longer or more often, tiredness, irritability, vomiting, and developmental delays. Many of these signs may occur when a baby eats foods the body cannot break down. Symptoms can be triggered by long periods of time without eating, illnesses, and infections.

Condition Type:

Core Conditions


Maple syrup urine disease (MSUD) affects 1 of every 185,000 babies born worldwide.

More Information for Parents:
Also known as:
  • MSUD
  • Ketoacidemia
  • Branched-chain alpha-keto acid dehydrogenase deficiency
  • Branched-chain ketoaciduria
  • BCKD deficiency

Core Conditions