A 9-month-old boy develops vomiting, lethargy, and hypoglycemia after introduction of fruit purees into his diet. He has an aversion to sweets. Liver function tests show elevated transaminases, and serum uric acid is high. Infusion of fructose precipitates hypoglycemia, hypophosphatemia, and a fall in serum potassium. Which enzyme is deficient?

• A Fructokinase
• B Aldolase B ✓
• C Triose kinase
• D Glucose-6-phosphatase

Explanation

Hereditary fructose intolerance results from aldolase B deficiency in liver, kidney, and intestine. Fructose-1-phosphate accumulates, trapping phosphate and impairing glycogenolysis and gluconeogenesis, hence hypoglycemia with hypophosphatemia. The striking aversion to sweet foods is characteristic because ingestion causes symptoms. Fructokinase deficiency causes essential fructosuria, a benign condition with fructose in urine but no hypoglycemia.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.