A 3-month-old infant has bilious vomiting, failure to thrive, and hepatomegaly since birth. Urine positive for reducing substances but urine glucose dipstick is negative. The reducing substance is NOT glucose. Which inborn error of metabolism is MOST consistent with this presentation?
- A Hereditary fructose intolerance
- B Classic galactosemia (GALT deficiency) ✓
- C Glycogen storage disease type I (von Gierke)
- D Maple syrup urine disease (MSUD)
Explanation
Classic galactosemia (GALT deficiency — galactose-1-phosphate uridylyl transferase) presents in neonates/early infants after milk feeding with jaundice, hepatomegaly, cataracts, E. coli sepsis, and failure to thrive. Urine shows a positive Clinitest (detecting galactose as a reducing substance) but negative glucose oxidase dipstick (glucose-specific), because galactose is not glucose. Both breast milk and cow's milk contain lactose (→ galactose + glucose), making galactosemia dangerous. Hereditary fructose intolerance occurs only after fructose/sucrose intake (rare in 3-month-olds). GSD I causes hypoglycemia with lactic acidosis but not reducing substances in urine. MSUD presents with maple syrup odor, not reducing sugars.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.