Maple syrup urine disease (MSUD) is an inherited disorder characterized by impaired protein metabolism, specifically the branched-chain amino acids leucine, isoleucine, and valine. The condition gets its name from the distinctive sweet odor of urine and earwax in affected infants.
MSUD is a rare disease, affecting an estimated 1 in 185,000 infants worldwide. While affecting any ethnicity, the disorder occurs much more frequently in certain ethnic groups, such as the Old Order Mennonite population with an estimated incidence of about 1 in 380 newborns, and the Ashkenazi Jewish population with an estimated incidence of 1 in 26,000 newborns.
A specialized medical formula provides all essential nutrients with the exception of the branched-chain amino acids leucine, isoleucine, and valine. These amino acids must be added to the diet in the precise amounts needed for normal growth and development. A strict diet and careful medical monitoring is essential throughout the lifespan.