Genetics
Maple Syrup Urine Disease (MSUD) is caused by a deficiency of the metabolic enzyme branched-chain α-keto acid dehydrogenase (BCKDH). This deficiency leads to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products in the blood and urine. Several forms of the disease include classic severe MSUD, intermediate MSUD, intermittent MSUD, thiamine-responsive MSUD and E3-Deficient MSUD with lactic acidosis. MSUD is inherited in an autosomal recessive manner.
Incidence
- Affects approximately 1 in 180,000 individuals
- There is a much higher incidence of MSUD in individuals of Amish and Mennonite descent
Symptoms/Characteristics
In infants, symptoms include:
- Sweet-smelling urine
- Poor feeding
- Vomiting
- Dehydration
- Lethargy
- Hypotonia
- Seizures
- Ketoacidosis
- Neurological decline
Clinical Management
- A diet with minimal levels of the amino acids leucine, isoleucine, and valine must be maintained in order to prevent neurological damage
- Specialized protein preparations containing substitutes and adjusted levels of the amino acids have been synthesized for use in individuals with MSUD