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October 12, 1963


JAMA. 1963;186(2):147. doi:10.1001/jama.1963.03710020067021

Maple syrup urine disease, first described in 1954, is one of the inborn errors of metabolism. Its name is derived from the characteristic odor of the urine. The basic defect is the absence of the enzyme that catalyzes the decarboxylation stage in the common metabolic pathway of the branched chain amino acids, leucine, isoleucine, and valine. This deficiency results in accumulation of these amino acids and their respective ketoacids in the blood, and gives rise to a so-called overflow amino-aciduria. These substances are believed to be responsible for the subsequent damage to the central nervous system. Thus, the disease parallels the situation that exists in phenylketonuria, in which an enzyme deficiency in one system results in damage to an unrelated system. The two diseases have identical urinary excretion patterns of the indoles, and each gives a characteristic positive urine test with ferric chloride. Severe brain damage, usually occurring in the

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