A previously healthy 8-month-old develops vomiting, sweating, and tremulousness about 30 minutes after being fed fruit puree for the first time. Blood glucose is 42 mg/dL, uric acid is elevated, and liver enzymes are mildly raised. Symptoms resolve completely with intravenous glucose. Introduction of sucrose-containing weaning foods produced an identical episode. Which enzyme deficiency is responsible?
- A Aldolase B ✓
- B Fructokinase
- C Fructose-1,6-bisphosphatase
- D Triose phosphate isomerase
Correct answer: A. Aldolase B
Explanation
Hereditary fructose intolerance results from aldolase A deficiency in liver, kidney, and intestine. Fructose-1-phosphate accumulates, trapping phosphate, depleting ATP, and secondarily inhibiting glycogenolysis and gluconeogenesis, causing post-ingestion hypoglycemia with vomiting and hyperuricemia. Fructokinase deficiency (essential fructosuria, option B) is benign and asymptomatic, which is the key distractor. Fructose-1,6-bisphosphatase deficiency produces fasting-induced, not fructose-triggered, hypoglycemia.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.