3-Ketothiolase deficiency.

Two patients have been studied in whom the activity of the short chain-length-specific mitochondrial 3-ketothiolase was found to be deficient. Use of a range of 3-ketoacyl-CoA substrates showed that the other 3-ketothiolase isoenzymes were normal in each case. Both patients had episodic ketosis and metabolic acidosis. One patient had substantial evidence of damage to the central nervous system and two siblings who had died of the disease. The organic aciduria was characterized by the excretion of 2-methyl-3-hydroxybutyric acid and tiglyglycine. In one patient the organic aciduria was very subtle and was masked during the presence of ketosis, but it was clarified by an isoleucine load after recovery from ketosis.