Peritoneal dialysis in maple-syrup-urine disease: Studies on branched-chain amino and keto acids

We report biochemical data on a child with MSUD who underwent peritoneal dialysis for severe metabolic imbalance. In confirmation of earlier data, the BCKA/BCAA ratios in blood had been found to be fairly stable in this patient during long-term dietary therapy.The child became comatose at comparatively low levels of leucine and KICA (ca. 2 mM each). At this time the blood/cerebrospinal fluid ratio for BCAA's and BCKA's was markedly diminished. During peritoneal dialysis, peritoneal clearance was highest for KIVA, but less for MEVA and BCAA's (40–50% or urea clearance), and least for the allegedly most toxic metabolite, KICA. The differences for BCKA's may be due to their differential protein binding. Given these individual differences, 1.8 to 8.7 initial plasma volumes were cleared in 14h with 24.21 of dialysis fluid. In the same time, urinary excretion of BCAA's and BCKA's was much less efficient.The data are discussed with regard to the pathobiochemical significance of high tissue levels of branched chain acids. A quantitative comparison between peritoneal dialysis and exchange transfusion is not yet possible.Abbreviations BCAA's branched-chain -amino acids - BCKA's branched-chain -keto acids - KICA -keto-isocaproic acid - KIVA -keto-isovalerio acid - MEVA -keto--methyl-n-valeric acid - MSUD maple syrup urine diseaseWith support of the Landesamt für Forschung des Ministeriums für Wissenschaft und Forschung des Landes Nordrhein-Westfalen. U.L. was supported by Deutsche Forschungsgemeinschaft, Bad Godesberg, G.F.R. (DFG La 201, Schwerpunkt Biochemische Humangenetik and SFB 33 Nervensystem und biologische Information)