Maple Syrup Urine Disease (MSUD)  is a disorder abnormally affecting the metabolism of amino acids.  This disease is treated and managed very similarly to the care of patients with PKU.

The disorder affects the way the body metabolizes certain components of protein. These components are the three branch-chain amino-acids leucine, isoleucine, and valine. These amino acids accumulate in the blood causing a toxic effect that interferes with brain function.

Inheritance and Frequency

The gene defect for MSUD is an autosomal recessive genetic trait and is unknowingly passed down from generation to generation.  This faulty gene usually emerges when two carriers have children together and pass it to their offspring.  For each pregnancy of two such carriers, there is a 25% chance that the child will be born with the disease and a 50% chance the child will be a carrier for the gene defect.

Studies conducted since 1979 (Georgia) show that MSUD affects approximately 1 in every 120,000 live births.  The frequency of MSUD is about 1 in 760 among Mennonites.  MSUD was first described as a disease in 1954.  It is believed to be in all ethnic groups worldwide.