Maple syrup urine disease is an inherited disorder in which the body is unable to process certain protein building blocks (amino acids) properly. The condition gets its name from the distinctive sweet odor of affected infants' urine. Beginning in early infancy, this condition is characterized by poor feeding, vomiting, lack of energy (lethargy), and developmental delay. If untreated, maple syrup urine disease can lead to seizures, coma, and death.
Maple syrup urine disease is often classified by its pattern of signs and symptoms. The most common and severe form of the disease is the classic type, which becomes apparent soon after birth. Variant forms of the disorder become apparent later in infancy or childhood and are typically milder, but they still involve developmental delay and other medical problems if not treated.
Maple syrup urine disease affects an estimated 1 in 185,000 infants worldwide. The disorder occurs much more frequently in the Old Order Mennonite population, with an estimated incidence of about 1 in 380 newborns.
Mutations in the BCKDHA, BCKDHB, DBT, and DLD genes cause maple syrup urine disease. These four genes provide instructions for making proteins that work together as a complex. The protein 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 four genes reduce or eliminate the function of the protein complex, preventing the normal breakdown of leucine, isoleucine, and valine. As a result, these amino acids and their byproducts build up in the body. Because high levels of these substances are toxic to the brain and other organs, their accumulation leads to the serious medical problems associated with maple syrup urine disease.
Read more about the BCKDHA, BCKDHB, DBT, and DLD genes.
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
These resources address the management of maple syrup urine disease and may include treatment providers.
You might also find information on treatment of maple syrup urine disease in
Educational resources and Patient support.
You may find the following resources about maple syrup urine disease helpful. These materials are written for the general public.
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- Additional NIH Resources - National Institutes of Health
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You may also be interested in these resources, which are designed for healthcare professionals and researchers.
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- Gene Tests - DNA tests ordered by healthcare professionals
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- PubMed - Recent literature
- Online Books - Medical and science texts
- OMIM - Genetic disorder catalog
- BCKD deficiency
- Branched-chain alpha-keto acid dehydrogenase deficiency
- Branched-Chain Ketoaciduria
- Ketoacidemia
- MSUD
The resources on this site should not be used as a substitute for
professional medical care or advice. Users seeking information about
a personal genetic disease, syndrome, or condition should consult with a qualified
healthcare professional.
See How can I find a genetics professional in my area? in the Handbook.