Maple Syrup Urine Disease

Our bodies are made up of both water and protein.  Amino acids are protein which come from meat, fish, dairy, eggs and whole grains. While consumption of protein effectively benefits many individuals, the negative aspect is also true and are linked to various diseases due to the improper: uptake,  absorption, degradation, or excretion of protein/amino acids within our bodies.  One disease, in which improper degradation of three amino acids valine, leucine and isoleucine, is identified with Maple syrup urine disease ((MSUD),  also called branched-chain ketoaciduria.)

Maple Syrup Urine Disease ( not linked to maple syrup) is a condition that gets its name from the distinctive sweet odor of affected infants’ urine.  MSUD is caused by a deficiency of  branched-chain alpha-keto acid dehydrogenase complex (BCKDH), which  leads to a buildup of the branched-chain amino acids (leucine, isoleucine and valine).  In other words, the build up of these amino acids in the blood and urine is toxic and dangerous for the body leading to neurological, muscular defects and death in infants and young children, if not identified when early symptoms present themselves.

In the right amounts , amino acids: valine, leucine and isoleucine benefit the body on a daily basis. The importance of valine promotes calm, mental health and muscle coordination. Leucine regulates how glucose is used by skeletal muscle and leucine also helps to maintain proper amounts of muscle protein in the body when normal amounts of leucine are not present in a persons diet. Isoleucine is critical for forming hemoglobin (red blood cells) and stabilizing and regulating blood sugar for an individuals energy level.

MSUD is characterized in an infant by the presence of sweet-smelling urine, with an odor similar to that of maple syrup. Infants with this disease seem healthy at birth, but if left untreated suffer severe brain damage and eventually die.  From early infancy, symptoms of the condition include poor feeding, vomiting, dehydration, lethargy, hypotonia, seizures, ketoacidosis, opisthotonus, pancreatitis, coma and neurological decline.

Maple syrup urine disease can be classified by its pattern of signs and symptoms, or by its genetic cause. The most common and severe form of the disease is the classic type, which appears soon after birth. Variant forms of the disorder may appear later in infancy or childhood and are typically less severe, but still involve mental and physical problems if left untreated.

There are several variations of the disease:

  • Classic Severe MSUD
  • Intermediate MSUD
  • Intermittent MSUD
  • Thiamine-responsive MSUD
  • E3-Deficient MSUD with Lactic Acidosis

Keeping MSUD under control requires on going regulation of blood and involves both a special diet and frequent testing.  A diet with minimal levels of the amino acids leucine, isoleucine, and valine must be maintained in order to prevent neurological damage. While these three amino acids (valine, leucine, isoleucine) are required for proper metabolic function in all people, specialized protein preparations containing substitutes and adjusted levels of the amino acids have been synthesized and tested, allowing MSUD patients to meet normal nutritional requirements without causing harm. Usually, patients are also monitored by both a doctor and dietitian. Ones diet must be strictly followed for life. However, with proper dietary management  many are able to live healthy, normal lives and not suffer the severe neurological damage associated with the disease.

Kim Crocker


  •  Podebrad F, Heil M, Reichert S, Mosandl A, Sewell AC, Böhles H (April 1999). “4,5-dimethyl-3-hydroxy-25H-furanone (sotolone)–the odour of maple syrup urine disease”. Journal of inherited metabolic disease 22 (2): 107–114. doi:10.1023/A:1005433516026. PMID 10234605
  •  Ogier de Baulny H, Saudubray JM (2002). “Branched-chain organic acidurias”. Semin Neonatol. 7 (1): 65–74. doi:10.1053/siny.2001.0087. PMID 12069539
  • Genetics Home Reference (GRH) – Genetic Conditions – Maple Syrup Urine Disease. GHR is a service of the U.S. National Library of Medicine. Reviewed February 2006; Published June 12, 2009
  •  Hallam P, Lilburn M, Lee PJ (2005). “A new protein substitute for adolescents and adults with maple syrup urine disease (MSUD)”. J. Inherit. Metab. Dis. 28 (5): 665–672. doi:10.1007/s10545-005-0061-6. PMID 16151896
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