Maple sugar urine disease

Wll. Westall, R. G., Dancis, J., and Miller, S., Maple sugar urine disease. 

As the name implies, the odor of urine in maple syrup urine disease (brancbed-chain ketonuria) suggests maple symp or burnt sugar. The biochemical defect involves the a-keto acid decarboxylase complex (reaction 2, Figure 30-19). Plasma and urinary levels of leucine, isoleucine, valine, a-keto acids, and a-hydroxy acids (reduced a-keto acids) are elevated. The mechanism of toxicity is unknown. Early diagnosis, especially prior to 1 week of age, employs enzymatic analysis. Prompt replacement of dietary protein by an amino acid mixture that lacks leucine, isoleucine, and valine averts brain damage and early mortality. 

In maple syrup urine disease, the branched-chain a-keto acid dehydrogenase that oxidatively decar-bo xylates the branched-chain amino acids is defective. As a result, the branched-chain amino acids and their a-keto analogs (produced by transamination) accumulate. They appear in the urine, giving it the odor of maple syrup or burnt sugar. The accumulation of a-keto analogs leads to neurologic complications. This condition is difficult to treat by dietary restriction, because abnormalities in the metabolism of three essential amino acids contribute to the disease. 

Maple syrup urine disease Sweat, urine, ear wax Maple syrup, burnt sugar... 

For example, alkaponuria is characterized by homogentisic acid in urine phenylketonuria, which results in mental retardation, is characterized by quantities of phenylpyruvic acid in the urine. It is diagnosed in a suspected patient by determining the amount of this acid in the urine and the increased levels of phenylalanine in the plasma. Maple sugar disease is diagnosed the presence of large amounts of the branched chain amino acids, such as valine, leucine, and isoleucine in the blood and urine. 

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