Workup of the Patient with Metabolic Acidosis and Massive Ketosis

Massive ketosis in a neonate or young infant is a key to the diagnosis of a classic organic aciduria. The initial episode may begin with vomiting, anorexia, and lethargy, but progresses rapidly to life-threatening acidosis, dehydration, coma, and apnea. A clinical clue to the diagnosis is metabolic acidosis with vomiting. Some infants with organic aciduria have been thought to have pyloric stenosis; similarly these infants are often thought to have sepsis. Septic infants can certainly be acidotic, but they are not ketotic. Testing of the urine for ketones is a must in all ill infants. Routine clinical chemistry reveals low pH, low bicarbonate, and an increased anion gap. The urine pH is low. Hyperchloremic acidosis and a normal anion gap mean intestinal losses or a renal tubular acidosis from other causes, the former with acidic urine and the latter with alkaline urine. Quantitative organic acid analysis by gas chromatography-mass spectrometry is essential in differential diagnosis which may be faster achieved by acylcarnitine (MS/MS) analysis.