What are the risks for maple syrup urine disease?

Brain damage: Maple syrup urine disease (msud) is caused by a gene defect. Persons with this condition cannot break down the Amino Acids leucine, isoleucine, and valine. This leads to a buildup of these chemicals in the blood. In the most severe form, msud can damage the brain during times of physical stress (such as infection, fever, or not eating for a long time). Some types of msud are mild however.