MSUD stands for "maple syrup urine disease". It's named for the sweet maple syrup smell of the urine in untreated babies. It is one type of amino acid disorder. People with this type of disorder have problems breaking down amino acids from the protein in the food they eat. Classic MSUD is caused by the absence of a group of enzymes called "branched-chain ketoacid dehydrogenase" (BCKAD). The job of this enzyme group is to break down three different amino acids called leucine, isoleucine, and valine. When they cannot be broken down these amino acids build up in the blood abd cause problems. These amino acids are "branched-chain amino acids" (BCAA) and are found in all foods that have protein. Large amounts are found in meat, eggs, milk and other dairy foods. Smaller amounts are found in flour, cereal, and some vegetables and fruits.