A 2-year-old boy presents with episodes of hypoglycemia triggered by fasting, hepatomegaly, and lactic acidosis. Glucagon fails to raise blood glucose. Fasting plasma reveals elevated lactate, pyruvate, alanine, and uric acid. Liver biopsy shows glycogen AND fat accumulation. The enzyme deficiency is:

• A Glucose-6-phosphatase (GSD Ia) ✓
• B Liver phosphorylase (GSD VI)
• C Debranching enzyme (GSD III)
• D Branching enzyme (GSD IV)

Explanation

GSD Ia (von Gierke disease) is characterized by hypoglycemia, lactic acidosis (pyruvate and lactate buildup as glucose-6-phosphate is shunted into glycolysis), hyperuricemia (from nucleotide degradation due to increased AMP), and combined glycogen plus fat accumulation in the liver (hepatic steatosis). Debranching enzyme deficiency (GSD III) causes milder disease without lactic acidosis. Phosphorylase deficiency (GSD VI) is also mild.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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Written and medically reviewed by the StethoPrep medical team.