Maple Syrup Urine Disease


Maple Syrup Urine Disease (MSUD) is a super rare condition in which the body is unable to break down certain proteins. MSUD is able to be diagnosed 12 hours from birth of an infant. It is classified as an Amino Acid Disorder because MSUD patients are not able to break down certain amino acids which are building blocks of proteins. It gets it's name from the unique sweet odor of an untreated baby.

Maple syrup urine disease (MSUD) affects one out of every 185,000 babies born worldwide. It is found in many countries throughout the world, although the condition is more common in certain ethnic groups. About one out of every 380 babies from the Old Order Mennonite population is affected by the condition. MSUD is also more common in people of French-Canadian ancestry and Ashkenazi Jewish ancestry.


  • MSUD
  • Branched-chain alpha-keto acid dehydrogenase deficiency
  • Branched-chain ketoaciduria
  • Ketoacidemia
  • BCKD deficiency


  • Distinctive sweet smell of affected urine
  • Poor feeding
  • Vomiting
  • Lack of energy
  • Developmental delay
  • If untreated; seizures, coma, death
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Metabolic Processes Involved

Decreased activity of the branched-chain alpha-ketoid dehydrogenase complex (BCKAD), which is the second enzymatic step in the degradative pathway of the BCAA's

BCKAD has four subunit components. Mutations in both alleles encoding any subunit can result in the decreased activity of the enzyme complex and the accumulation of BCAA's and corresponding BCKA's in tissues and plasma

Support Groups

MSUD Family Support Group