A previously well 8-month-old develops vomiting, sweating, tremulousness, and hypoglycemia about 30 minutes after being given fruit juice for the first time. Blood shows hypophosphatemia but lactate is only mildly raised. Introduction of sucrose-containing weaning foods had caused similar episodes. The defective enzyme is:
- A Aldolase B ✓
- B Fructokinase
- C Fructose-1,6-bisphosphatase
- D Triose kinase
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 and causing ATP depletion, hypoglycemia, hypophosphatemia, and vomiting after fructose or sucrose ingestion. Fructokinase deficiency (essential fructosuria) is benign with only urinary fructose, and fructose-1,6-bisphosphatase deficiency causes hypoglycemia with pronounced lactic acidosis even without fructose intake, triggered by fasting.
Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.