Unusual Metabolites in a Patient with Isovaleric Acidemia.

A 3-day-old female infant was brought to the emergency room following an abnormal newborn screening showing markedly increased isovaleryl/2-methylbutyryl carnitine levels (C5; 23.11 μmol/L; reference interval, u003c0.60 μmol/L) and C5/C2, C5/C0, and C5/C3 ratios. At admission, the patient presented with bradycardia and hypothermia (95.4 °F) and was treated with intravenous fluids. Routine biochemistry testing indicated mild metabolic acidosis (total CO2, 16.6 mmol/L; reference interval, 21–29 mmol/L) and an anion gap of 23 mmol/L. Plasma ammonia was high (168 μmol/L; reference interval, u003c90 μmol/L) and rose further within a few hours to 445 μmol/L, requiring therapy with sodium phenylacetate/sodium benzoate (Ammonul). No unusual odor was noted from the child or the childu0027s urine. Follow-up plasma acylcarnitine analysis by tandem mass spectrometry confirmed the increased C5 (10.98 μmol/L; reference interval, u003c0.30 μmol/L). Moreover, to identify the specific defect, a urine sample was sent for organic acid analysis by GC-MS and for acylglycine analysis by liquid chromatography–tandem mass spectrometry. Results of the urine organic acid analysis are shown in Fig. …