Maple syrup urine disease

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Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disorder due to a deficiency of Branched chain α-keto acid dehydrogenase (BCKDH) that leads to elevated concentrations of leucine, isoleucine, and valine (branched amino acids) in the blood and urine. Characterized by the urine having an odor similar to that of maple syrup, this results in severe mental retardation, and seizures. Because of a genetic bottleneck effect, MSUD has a much higher prevalence in children of Amish and Mennonite descent. Also called branched chain ketoaciduria.

From early infancy, the condition is characterized by poor feeding, vomiting, lack of energy (lethargy), seizures, and mental health issues. The urine of affected infants has a distinctive sweet odor, much like burned caramel, that gives the condition its name. Maple syrup urine disease can be life-threatening if left untreated.

Maple syrup urine disease can be classified by its pattern of signs and symptoms or by its genetic cause. The most common and most severe form of the disease is the classic type, which appears soon after birth. Variant forms of the disorder appear later in infancy or childhood and are typically less severe, but still involve mental and physical retardation if not treated.

There are several variations of the disease:

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

1 Treatment
2 Genetics
3 In fiction
4 Reference
5 External links

[edit] Treatment

Treatment of the MSUD, like diabetes, requires careful monitoring of blood chemistry and involves both 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. Usually, patients, or parents of patients are assisted by a physician or dietician. This diet must be adhered to strictly and permanently. However, with proper treatment those afflicted are able to live healthy, normal lives and not suffer the severe neurological damage that characterizes the untreated disease.

[edit] Genetics

Image:Autorecessive.jpg

Maple syrup urine disease affects an estimated 1 in 185,000 infants worldwide.

Mutations in the following genes cause maple syrup urine disease:

BCKDHA (Mendelian Inheritance in Man (OMIM) 608348)
BCKDHB (Mendelian Inheritance in Man (OMIM) 248611)
DBT (Mendelian Inheritance in Man (OMIM) 248610)
DLD (Mendelian Inheritance in Man (OMIM) 238331)

23:41, 28 November 2006 (UTC)~These four genes produce proteins that work together as the branched-chain alpha-keto acid dehydrogenase complex. The complex is essential for breaking down the amino acids leucine, isoleucine, and valine, which are present in many kinds of food (particularly protein-rich foods such as milk, meat, and eggs). Mutations in any of these genes reduce or eliminate the function of the enzyme complex, preventing the normal breakdown of leucine, isoleucine, and valine. As a result, these amino acids and their by-products build up in the body. Because high levels of these substances are toxic to the brain and other organs, this accumulation leads to the serious medical problems associated with maple syrup urine disease. However recent breakthroughs have yielded treatments through liver transplants and gene therapy is on the rise.