Ketones

- An insight into the biochemistry of inborn errors of metabolism for a clinical neurologist

Ketonuria is a physiological finding in many cases of late infancy, childhood and even adolescence. Ketosis, which is not associated with acidosis, hyperlactacidemia or hypoglycemia, is likely to be a normal physiological indication of the nutritional state (fasting, catabolism, vomiting, medium-chain triglyceride-enriched or other ketogenic diets). It may be the cause or consequence of repeated vomiting in infants and children. However, hyperketosis at a level that produces metabolic acidosis is not physiological. Hyperglycemia associated with ketosis indicates the presence of diabetes mellitus.

Ketolytic defects (succinyl-CoA: oxo-acid transferase and 3-ketothiolase deficiencies) can present as moderate ketonuria occurring mainly in the fed state at the end of the day.^[32] Severe fasting ketonuria without acidosis is often observed in debrancher, and glycogen synthase deficiencies. In both disorders, hepatomegaly, fasting hypoglycemia and postprandial hyperlactacidemia are observed. Ketosis without acidosis is also observed in ketotic hypoglycemias due to adrenal insufficiency, hyperinsulinemic states at any age and growth hormone deficiency in infancy.