An infant or child presenting with acidosis and/or ketosis may have an inborn error of metabolism or simply a physiologic response to fasting, vomiting or diet. By looking at the pattern of laboratory test findings some possible explanations for the patient's condition can be identified.
Presenting groups:
(1) metabolic acidosis with ketosis
(2) metabolic acidosis without ketosis
(3) ketosis without metabolic acidosis
Metabolic acidosis:
(1) pH < 7.30
(2) PCO2 < 30 mm Hg
(3) serum bicarbonate < 15 mmol/L (mEq/L)
Ketosis: ketonuria, increase in ketone bodies
Metabolic Acidosis with Ketosis
Glucose Levels |
Additional Testing |
Diagnostic Considerations |
increased |
high ammonia |
ketolytic defects |
increased |
normal or low ammonia |
branched chain organic acidurias |
normal |
high lactate |
congenital lactic acidosis respiratory chain disorders organic acidurias |
normal |
normal lactate |
maple syrup urine disease, late onset form ketolytic defects organic acidurias short chain acylCoA dehydrogenase |
decreased |
high lactate often with hepatomegaly |
gluconeogenesis defects respiratory chain defects |
decreased |
normal lactate |
maple syrup urine disease, late onset form branched chain organic acidurias acetoacetyl CoA thiolase adrenal insufficiency |
Metabolic Acidosis without Ketosis
Lactate |
Glucose |
Diagnostic Considerations |
increased |
normal |
pyruvate dehydrogenase deficiency |
increased |
decreased |
fatty acid oxidation disorders hydroxymethylglutaryl-CoA lyase glucose 6 phosphatase deficiency fructose biphosphatase deficiency |
normal |
normal |
renal tubular acidosis I and II pyroglutamic aciduria |
Ketosis without Metabolic Acidosis
Glucose Levels |
Additional Testing |
Diagnostic Considerations |
normal glucose |
intermittent ketosis |
fasting catabolism recurrent vomiting (physiologic ketonuria) short chain acyl CoA dehydrogenase hydroxy short chain acyl dehydrogenase |
normal glucose |
permanent ketosis |
medium chain triglyceride enriched diet and ketotic diet ketolytic defects |
fasting hypoglycemia |
with hepatomegaly and post-prandial hyperlactacidemia |
glycogenosis type III glycogen synthetase deficiency |
fasting hypoglycemia |
without hepatomegaly |
recurrrent ketotic hypoglycemia hypoglycemia due to adrenal disorders hydroxy short chain acyl dehydrogenase medium chain acyl CoA dehydrogenase glycogen synthetase deficiency ketolytic defects |
ketolytic defects: oxoacyltransferase deficiency, thiolase deficiency
branched chain organic acidurias: methylmalonic acid (MMA), propionic acid (PA), isovaleric acid (IVA)
congenital lactic acidosis: pyruvate carboxylase (PC) deficiency, multiple carboxylase deficiencies, ketoglutarate dehydrogenase (KGDH) deficiency, lipoamide oxidoreductase (E3) deficiency
gluconeogenesis defects: fructose diphosphatase (FDP) deficiency, glucose 6 phosphatase (G6P) deficiency, glycogen synthase deficiency
organic acidurias: 3-hydroxyisobutyric aciduria, others
Specialty: Endocrinology, Clinical Laboratory, Genetics
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