Hyperammonia has been reported in several disorders of branched chain amino acid metabolism including propionic, isovaleric, methylmalonic acidemia, and β-ketothiolase deficiency.1 Nevertheless the true incidence of hyperammonemia and its variation during the course of these diseases are not yet well known. The purpose of this study was to compare the blood ammonia concentrations and the concomitant serum organic acid accumulation in patients with propionic and isovaleric acidemia.


Seven patients with propionic acidemia have been studied. The diagnosis was usually made during the first episode of the disease by gas chromatography. It was always confirmed by the direct measurement of propionyl coenzyme A (CoA) carboxylase activity in fibroblasts.2

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