Maple Syrup Urine Disease

by Stephanie Guiffrida, , April 28, 2010

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Maple syrup urine disease (MSUD), also called branched-chain ketoaciduria, is an autosomal recessive metabolic disorder affecting branched-chain amino acids that build up due to the body being unable to break down certain parts of proteins such as the three amino acids: leucine, isoleucine, and valine. They are normally broken down by six proteins that act as a team and form a complex called BCKD (branched-chain alpha-ketoacid dehydrogenase). Leucine, isoleucine, and valine are present in many kinds of food, particularly protein-rich foods such as milk, meat, and eggs. This inability to break down amino acids leads to a buildup of these toxic chemicals in the blood. Maple syrup urine disease affects approximately 1 in every 180,000 infants and is characterized by distinctive sweet-smelling urine, a smell similar to that of maple syrup.

The most common, severe case of MSUD occurs in infants soon after birth. Some cases may occur later in childhood but are much milder cases. This inherited disease is passed down from generation to generation when parents each carry one copy of the mutated gene. The parents are typically unaffected and do not show any signs or symptoms. Recognizing MSUD immediately is very crucial. Infants that are not diagnosed with maple syrup disease until later in life and left untreated may suffer from severe brain damage, seizures, coma, and even death due to the accumulation of high levels of toxic substances affecting the brain and other organs. Signs and symptoms include: vomiting, poor feeding, lethargy, neurological decline, acidosis, and the previously mentioned maple-syrup scented urine.

How is MSUD diagnosed? It is now very common for doctors to require blood tests for all infants to test for MSUD. Two tests that are performed are a plasma amino acid test and a urine amino acid test. If families have a history of MSUD and plan on having children, it is necessary to seek a genetic counselor to help find out the possibilities of them having an infant with MSUD.

How is MSUD treated? If diagnosed with maple syrup urine disease as an infant, it can be treated with a protein-free diet. A dietitian can alter the diet based on specific amino acid levels. Sugars, fats, and fluids and given through a vein due to the difficulty of feeding thought the mouth. A long term treatment includes a permanent diet of a formula with low levels of leucine, isoleucine, and valine. With immediate diagnosing and a strict dietary treatment, many infants with MSUD can grow into healthy functioning adults.

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