Maple syrup urine disease
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| Maple syrup urine disease Classification and external resources | |
 | |
|---|---|
| Leucine (pictured above), isoleucine, and valine are the branched-chain amino acids which build up in MSUD. | |
| ICD-10 | E71.0 |
| ICD-9 | 270.3 |
| OMIM | 248600 |
| DiseasesDB | 7820 |
| MedlinePlus | 000373 |
| eMedicine | ped/1368 |
| MeSH | D008375 |
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Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disorder of amino acid metabolism. It is also called branched chain ketoaciduria.
Causes
This amino acid acidopathy is due to a deficiency of the metabolic enzyme branched chain α-keto acid dehydrogenase (BCKDH) leading to a buildup of branched-chain amino acids (leucine, isoleucine, and valine) in the blood and urine.
Presentation
Characterized by an infant with 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. Because of the founder effect, MSUD has a much higher prevalence in children of Amish and Mennonite descent. [1] [1]
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.
Classification
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
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.
Genetics
Maple syrup urine disease affects an estimated 1 in 185,000 infants worldwide.
Mutations in the following genes cause maple syrup urine disease:
- BCKDHA (Online 'Mendelian Inheritance in Man' (OMIM) 608348)
- BCKDHB (Online 'Mendelian Inheritance in Man' (OMIM) 248611)
- DBT (Online 'Mendelian Inheritance in Man' (OMIM) 248610)
- DLD (Online 'Mendelian Inheritance in Man' (OMIM) 238331)
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.
See also
References
Additional Resources
- Overview of condition at NLM Genetics Home Reference
External links
- 1483407370 at GPnotebook
- msud at NIH/UW GeneTests
- Maple Syrup Urine Disease (Overview on NLM)
- MSUD Family Support Group|[3]
fr:Maladie du sirop d'érable ms:Penyakit Kencing Sirap Maple
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
