An infant develops severe vomiting, lethargy, and marked ketoacidosis after weaning from night feeds. Urine organic acid analysis shows large amounts of acetoacetate and beta-hydroxybutyrate. Enzyme assay confirms succinyl-CoA:3-ketoacid CoA-transferase (SCOT) deficiency. The expected laboratory finding distinguishing this disorder from ketolytic defects elsewhere is:
- A Normal ketone production by the liver with inability of extrahepatic tissues to use ketones ✓
- B Hypoketotic hypoglycemia during fasting
- C Elevated C8 acylcarnitines on tandem mass spectrometry
- D Accumulation of methylmalonic acid in plasma
Correct answer: A. Normal ketone production by the liver with inability of extrahepatic tissues to use ketones
Explanation
SCOT catalyzes the first step of extrahepatic ketone utilization, converting acetoacetate to acetoacetyl-CoA. In SCOT deficiency the liver synthesizes ketones normally, producing frank ketoacidosis rather than hypoketotic hypoglycemia, which instead signals impaired ketone production as in MCAD deficiency. Elevated medium-chain acylcarnitines point to a beta-oxidation defect, and methylmalonic aciduria indicates a propionate pathway block.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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