Maple Syrup Urine Disease
Maple syrupe urine disease (MSUD) is an autosomal recessive metabolic disorder that leads to the accumulation of branched-chain amino acids. Infants with maple syrup urine disease have urine with a distinctive sweet odor that is reminiscent of maple syrup. This sweet-smelling urine is usually noticed prior to diagnosis and during acute disease. MSUD is caused by a defect in branched-chain ketoacid dehydrogenase, which leads to the accumulation of isoleucine, leucine, and valine. This accumulation of branched-chain amino acids leads to a number of CNS problems: developmental delay, lethargy, and posturing (decorticate or decerebrate). If left untreated, patients usually die in infancy. Since thiamine pyrophosphate (TPP) is a cofactor for branched-chain ketoacid dehydrogenase, some forms of maple syrup urine disease may improve and be treated with thiamine (vitamin B1).