Glycolytic Enzyme Regulation and Deficiencies

A 6-month-old girl from Delhi is brought to the pediatric emergency with a history of vomiting, abdominal pain, and hypoglycemia (blood glucose 38 mg/dL) that developed 2 hours after her mother fed her honey and fruit juice. On examination, she is irritable with hepatomegaly. Serum fructose is markedly elevated. Liver function tests show elevated transaminases (AST 320 U/L, ALT 280 U/L) and hyperbilirubinemia. Which enzyme deficiency best explains this acute presentation?

A 3-year-old boy from rural Maharashtra presents with severe hypoglycemia (blood glucose 35 mg/dL), hepatomegaly, and lactic acidosis (pH 7.2, lactate 8 mmol/L) following a 6-hour fast. Clinical suspicion is high for a glycolytic enzyme deficiency. Which investigation is most specific for confirming phosphofructokinase (PFK) deficiency?

A 28-year-old woman with a history of recurrent muscle pain, myoglobinuria after exercise, and normal fasting glucose presents to the metabolic clinic. Serum CK is markedly elevated (8500 U/L). Suspicion is raised for pyruvate kinase (PK) deficiency. Which investigation is most appropriate to confirm the diagnosis?

A 3-year-old boy from rural Maharashtra presents with severe hypoglycemia (blood glucose 35 mg/dL) and hepatomegaly during fasting. Enzyme assay shows deficiency of glucose-6-phosphatase. His older sister, diagnosed at age 2, has normal fasting glucose but recurrent muscle pain and dark urine after exercise. Which feature best distinguishes the sister's condition from the boy's?

A 3-year-old boy from rural Maharashtra presents with severe hypoglycemia, hepatomegaly, and lactic acidosis following a 4-hour fast. Genetic testing reveals a deficiency in a glycolytic enzyme. Which enzyme deficiency is the most common cause of glycolytic enzyme deficiency presenting with this clinical picture?