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