Maple syrup urine disease (MSUD) is a genetically inherited metabolic disease. Its name is derived from one of the hallmark symptoms—urine that smells like maple syrup. MSUD is caused by a mutation of four genes—BCKDHA, DLD, BCKDHB and DBT—that are involved in protein production. As a result, the patient cannot process three types of amino acids: valine, leucine and isoleucine. Unable to be broken down, the chemicals build up in the patient's blood. MSUD has an autosomal recessive pattern of inheritance, meaning that the patient must receive a copy of the mutated genes from each parent.
MSUD is a rare disease that starts during infancy, affecting one in 185,000 children in the world, according to the ]]>Genetics Home Reference]]>; however, MSUD has a higher rate of incidence in the Old Order Mennonite population, affecting one in 380 infants. Besides the sweet smelling urine, the patient can also experience vomiting and lethargy. Parents will notice that their child is avoiding food and has problems eating. Other serious symptoms include seizures and a coma. Untreated MSUD can result in brain damage, causing some patients to have developmental delays.