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Maple Syrup Urine Disease, or branched-chain ketoaciduria is a metabolic, genetic disease that results from defective enzyme activity. Defective branched chain alpha-ketoacid dehydrogenase complex affects the metabolism of essential branched-chain amino acids leucine, isoleucine, and valine. The prevalence of this autosomal recessive disorder is 1:200,000. The prevalence of intermittent MSUD is rare. The most common form of MSUD appears 4-5 days after birth. Biochemical features include seizures, acidosis, intermittent symptoms, and plasma leucine, isoleucine, and valine ten times normal.

Genetic Factors Genes that are affected with MSUD and organic acidemias are branched chain ketoacid dehydrogenase E1, alpha & beta polipeptide, dihydrolipoamide branch chain transacylase E2, and dihydrolipoamide dehyrdogenase. These four genes code for the enzyme brainced chain alpha ketoacid dehydrogenase complex that is essential to break down the amino acids leucine, isoleucine, and valine. Defective genes reduce the ability of the enzyme to metabolism these amino acids leading to their buildup in the body. Maple syrup urine disease results from the high level of these amino acids that are toxic to the brain and organs.

Characteristic Signs & Symptoms Infants affected by this disease may suffer from vomiting, lethargy, poor feeding and hypertonia (muscle spasticity associated to damage to central nervous system). The sweet, maple odor in the urine and perspiration is what gives the disease its characteristic name.

Diet Therapy Dietary recommendations include a low protein diet and soy based formulas without leucine, isoleucine and valine. Formulas that provide a mix of amino acids and vitamins are now available. Some may require supplemented standard infant formula or cows milk to have BCAA required for growth.

Treatment Treatment of acute disease usually require peritoneal dialysis and hydration. Thiamin supplementation can be beneficial. Acidosis, neurologic degeneration, seizure, coma, and even death can result if MSUD is left untreated.