A 6-year-old boy from rural Maharashtra presents with recurrent episodes of severe hypoglycemia, hepatomegaly, and lactic acidosis after fasting for 4 hours. Genetic testing reveals a deficiency in glucose-6-phosphatase. Regarding the metabolic consequences of this enzyme deficiency, all of the following are TRUE EXCEPT:

Explanation

## Glucose-6-Phosphatase Deficiency (Type I Glycogen Storage Disease / Von Gierke Disease) ### Overview Glucose-6-phosphatase catalyzes the final step of both gluconeogenesis and glycogenolysis: $$\text{Glucose-6-phosphate} \xrightarrow{\text{G6Pase}} \text{Glucose} + \text{Pi}$$ Without this enzyme, the body cannot release free glucose into the bloodstream, causing severe fasting hypoglycemia and metabolic derangements. ### Metabolic Consequences of G6Pase Deficiency | Consequence | Mechanism | Clinical Result | |-------------|-----------|----------------| | **G6P accumulation** | Cannot be converted to free glucose | Shunted to glycogen synthesis and pentose phosphate pathway | | **Fasting hypoglycemia** | Cannot complete gluconeogenesis or glycogenolysis | Severe hypoglycemia within 3–4 hours of fasting | | **Lactic acidosis** | G6P → glycolysis → pyruvate → lactate (no glucose release to feedback-inhibit) | Elevated lactate, low pH | | **Hepatomegaly** | Glycogen accumulation + increased lipogenesis from excess G6P | Massive liver enlargement | | **Hyperuricemia** | Increased purine degradation from high ATP turnover | Gout, uric acid nephropathy | | **Hyperlipidemia** | Excess G6P → acetyl-CoA → fatty acid synthesis | Elevated triglycerides and cholesterol | **Key Point:** Lactate and alanine produced in this condition **cannot** be efficiently converted back to glucose because the final step (G6P → glucose) is blocked. This creates a vicious cycle: lactate accumulates and causes acidosis; gluconeogenesis is futile because the product cannot be released. **High-Yield:** Von Gierke disease (G6Pase deficiency) is the most severe glycogen storage disease and the only one that causes severe fasting hypoglycemia and lactic acidosis together. **Clinical Pearl:** Patients require frequent feeding (every 2–3 hours) or continuous nasogastric feeding with uncooked cornstarch to maintain glucose homeostasis. They cannot fast safely. ### Why Option 2 (Lactate Conversion) is Incorrect Option 2 claims that "lactate and alanine are efficiently converted to glucose via gluconeogenesis, preventing lactic acidosis." This is **false**. Although the enzymes of gluconeogenesis are present and functional, they produce glucose-6-phosphate, which cannot be converted to free glucose because glucose-6-phosphatase is deficient. Therefore: 1. Lactate → pyruvate → oxaloacetate → PEP → ... → G6P (blocked) 2. G6P accumulates and cannot be released as glucose 3. Lactate continues to accumulate → lactic acidosis 4. Gluconeogenesis becomes futile and actually worsens the metabolic problem This is a **futile cycle** — lactate is produced but cannot be cleared efficiently, and attempted gluconeogenesis only produces more G6P, which is shunted back to glycolysis and lactate production.