Investigation of enzyme defects in children with lactic acidosis.

Screening for enzyme deficiencies was carried out in cultured skin fibroblasts and leukocytes of 19 patients with lactic acidosis and neurological problems. Pyruvate carboxylase deficiency was demonstrated in three cases. Reduced pyruvate oxidation was found in seven cultures; six showed no significant stimulation of the oxidation rate by methylene blue and in three a decreased pyruvate dehydrogenase complex activity was confirmed. Methylene blue restored a near normal oxidation rate in the seventh culture which had decreased cytochrome c oxidase activity.