Organic acids in urine of patients with congenital lactic acidoses: an aid to differential diagnosis.

The differential diagnosis of patients with apparent congenital lactic acidoses poses one of the most intractable problems in the study of patients with disorders of organic acid metabolism. An outline of the factors leading to a lactic acidosis, particularly in infants and young children, together with a brief review of the known causes of congenital lactic acidosis, are presented. Quantitative examination of the organic acids excreted by patients with proven enzyme deficiencies causing congenital lactic acidosis has demonstrated the characteristic patterns that are associated with specific disorders of this kind. After exclusion of uninherited, acquired and secondary metabolic causes of lactic acidosis, the quantitative patterns of organic acid excretion, together with other clinical and biochemical observations, provide valuable indicators of the area of the underlying primary metabolic disorder for subsequent selected, confirmatory, enzymology. The study of organic acids has a key and central role in the approach to the clinical and biochemical investigation and diagnosis of patients with congenital lactic acidoses.