A child rapidly develops hypoglycemia after moderate activity. On physical examination, kidney and liver are found to be enlarged. Histopathology of liver shows deposits of glycogen in an excess amount. Blood examination reveals raised ketone bodies, lactic acid and triglycerides. Which enzyme is deficient in this patient?

**Core Concept:**
Hypoglycemia is a condition characterized by low blood glucose levels. In this scenario, a child develops hypoglycemia after moderate activity and has enlarged kidneys and liver on examination. The liver histopathology shows excess glycogen deposits, elevated ketone bodies, lactic acid, and triglycerides in the blood. These findings suggest a disorder of glycogen storage and utilization in the liver.

**Why the Correct Answer is Right:**
In this case, the child has a deficiency of the enzyme Phosphofructokinase-1 (PFK-1), which is an important enzyme involved in glycolysis, the initial step in the breakdown of glucose into pyruvate. PFK-1 deficiency leads to reduced glycolysis and increased glycogen storage in the liver, resulting in hypoglycemia and the other clinical and laboratory findings described.

**Why Each Wrong Option is Incorrect:**
A. Glycogen synthase deficiency (GSD-III): Glycogen synthase deficiency results in impaired glycogen synthesis, not deficiency of PFK-1, which is the correct answer.
B. Phosphoglucomutase-1 (PGM-1) deficiency: PGM-1 deficiency affects the last step in glycogen breakdown, not PFK-1 deficiency, which is the correct answer.
C. Phosphofructose kinase deficiency (PFK): PFK deficiency affects the first step in glycolysis, not PFK-1 deficiency, which is the correct answer.
D. Pyruvate kinase deficiency: Pyruvate kinase deficiency is related to the last step in glycolysis, not PFK-1 deficiency, which is the correct answer.

**Clinical Pearl / High-Yield Fact:**
Phosphofructokinase-1 deficiency is an example of a hereditary enzyme deficiency that can present with hypoglycemia, liver enlargement, elevated ketone bodies, lactic acid, and triglycerides. This condition should be considered in the differential diagnosis of pediatric hypoglycemia, especially when associated with hepatomegaly and ketosis.

✓ Correct Answer: C. Glucose-6-phosphatase