Fatal lactic acidosis in a newborn attributable to a congenital defect of pyruvate dehydrogenase.

An infant suffering from metabolic acidosis attributable to hyperlactatemai (6.1 mmol/liter) accompanied by hyperalaninemia (1 mmol/liter) and hyperserinemia (0.6 mmol/liter) is described. The urinary excretion of lactate and pyruvate was greatly elevated; the lactate to pyruvate ratio was normal. The urine showed low levels of citrate, isocitrate, and cis-aconitate, and low or normal levels of alpha-oxoglutarate, succinate, malate, and methylmalonate. Aspartate was slightly elevated in serum and urine, indicating a corresponding increase if its alpha-ketoacid oxaloacetatae. These patterns of organic acids and amino acids suggested an in vivo defect in the oxidation of pyruvate. Fibroblasts cultured from skin biopsy from the patient metabolized radioactive pyruvate (final concentration 0.04-2 mmol/liter) to CO2 at rates from 5 to 17% of that of fibroblasts from normal control subjects. Enzyme studies with fibroblast sonicates revealed a severe deficiency of the pyruvate dehydrogenase complex (about 8% of normal), and this error was localized to the first unit of the complex, i.e., the pyruvate dehydrogenase (about 4% of normal). Fibroblasts from both parents metabolized pyruvate to CO2 at a slightly reduced rate, suggesting parental heterozygosity.