No abstract

Pediatr. Res. 14: 956-962 (1980) SummaryA total of 40 skin fibroblast cultures from pediatric cases of lactic acidosis were subjected to a series of tests designed to elucidate the nature of an underlying defect in metabolism. Of these 40 cases, in 14 we were able to define the following problems.Pyruvate carboxylase deficiency was evident in five cases showing <10% normal activity. Phosphoenolpyruvate carboxykinase deficiency was evident in one case where the whole cells showed 17% of normal activity whereas the mitochondria1 activity of this enzyme was 6% of normal. Pyruvate dehydrogenase deficiency was present in six cases showing 8 to 39% of normal activity, five of them being due to deficient pyruvate decarboxylase activity and one of them being due to deficient dihydrolipoyl dehydrogenase activity. Two cases were found with normal enzymes of pyruvate metabolism in which the production of '4COz from was deficient at 13 and 28% of normal activity, respectively, which we consider to be indicative of reduced activity of the Krebs' cycle. The grounds for the diagnosis of these 14 affected cases are documented, and the clinical presentation of these enzyme deficiencies is assessed in the light of present knowledge about lactic acidosis. Speculation years, the diagnosis being made most commonly on measurement of enzyme activity on a liver biopsy specimen. Where phosphoenolpyruvate carboxykinase (PEPCK) and pymvate carboxylase deficiencies are concerned, the number of cases are few, and the associated symptoms not always similar. Two diagnoses have been made based on the measurement of pyruvate carboxylase activity in fibroblasts (1, 10); in other cases, the diagnosis has been made on liver biopsy (29,31,33,35). Three cases of PEPCK deficiency have been documented, in two of which the localization of the defect is not specified (13,15). and in one of which the cytosolic PEPCK is identified as the missing component (36).Fatal lactic acidosis has been described in which postmortem examination of muscle tissue showed in one case deficient cytochrome aa3 and cytochrome b (34), and in another case, deficient cytochrome aas (38). In both cases, the defect seemed to be confined to skeletal muscle.We present here the results of our studies on the skin fibroblasts from 40 new patients with lactic acidosis and attempt to correlate identifiable metabolic deficiencies with clinical presentation. fetal calf semm added. Confluent cells were harvested with 0.025% tetramer, dihydrolipoyl transacet~lase, and d i h~d r o l i~o~l dehy-trypsin. Cells used for studies were washed free of trypsin by drogenase (Ed. although there is a specific kinase and a ~h o s~h a -repeated ( X 3) centrifugation and resuspension of the packed cells tase modulating the activity of El (9. 26, 37). At least nine in phosphate-buffered saline. confirmed cases of El deficiency have been described (3, 5, 6, 11, 12. 30). A presumptive, but unproven, diagnosis of dihydrolipoyl WHOLE-CELL ASSAYS transacetylase deficiency has been made (8), and two cases...