Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ Key Features ++ Typical presentation is infantile encephalopathy Due to deficiency of the enzyme that catalyzes the oxidative decarboxylation of the branched-chain keto acid derivatives of leucine, isoleucine, and valine Accumulated keto acids of leucine and isoleucine cause the characteristic sweet odor Only leucine and its corresponding keto acid have been implicated in causing central nervous system (CNS) dysfunction Many variants of this disorder have been described, including mild, intermittent, and thiamine-dependent forms All are autosomal recessive traits +++ Clinical Findings ++ Patients are normal at birth Feeding difficulties, coma, and seizures develop after about 1 week Nearly normal growth and development may be achieved if treatment is begun before about age 10 days, which is facilitated by newborn screening +++ Diagnosis ++ Amino acid analysis shows marked elevation of branched-chain amino acids including alloisoleucine, a diagnostic transamination product of the keto acid of isoleucine Urine organic acids demonstrate the characteristic keto acids The magnitude and consistency of metabolite changes are altered in mild and intermittent forms Prenatal diagnosis is possible by enzyme assay in cultured amniocytes or chorionic villi, and by molecular analysis if the mutation is known Unless diagnosis is made and dietary restriction of branched-chain amino acids is begun, most infants will die in the first month of life +++ Treatment ++ Dietary leucine restriction and avoidance of catabolism are the cornerstones of treatment Infant formulas deficient in branched-chain amino acids must be supplemented with normal foods to supply enough branched-chain amino acids to permit normal growth Plasma levels of branched-chain amino acids must be monitored frequently to deal with changing protein requirements Acute episodes must be aggressively treated to prevent catabolism and negative nitrogen balance Very high leucine levels require hemodialysis Liver transplantation corrects the disorder Your Access profile is currently affiliated with [InstitutionA] and is in the process of switching affiliations to [InstitutionB]. Please select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free profile for additional features.