What will be the likely diagnosis in a child with massive hepatomegaly and hypoglycemia, whose blood glucose shows no improvement on administration of glucagon?
First, hypoglycemia in children can be due to several causes. Common ones include glycogen storage diseases, insulinoma, or other metabolic issues. The fact that glucagon doesn't work is a key clue. Glucagon stimulates glycogenolysis and gluconeogenesis. If the liver can't respond to glucagon, maybe there's a problem with glycogen storage or gluconeogenesis enzymes.
Massive hepatomegaly points towards a storage disorder. Glycogen storage diseases (GSDs) come to mind. For example, GSD type I (von Gierke's disease) is caused by a deficiency in glucose-6-phosphatase. This enzyme is crucial for the final step in gluconeogenesis and glycogenolysis. Without it, the liver can't release glucose, leading to hypoglycemia. The liver becomes enlarged due to excess glycogen and lipid accumulation. Also, glucagon and epinephrine won't help because they can't bypass the missing enzyme.
Other GSDs might be considered. Type III (Cori's disease) has a deficiency in debranching enzyme, but the liver can still release glucose via glucose-6-phosphatase. So glucagon might still work here. Type II (Pompe's disease) is a lysosomal storage disease, causing cardiomegaly and hypotonia, not typically massive hepatomegaly. Type V (McArdle's disease) affects muscle, not liver.
So the correct answer should be GSD type I. The other options either involve different enzymes or present with different features. The lack of response to glucagon is a classic sign of GSD I because the enzyme needed to release glucose is missing.
**Core Concept**
This question tests understanding of **glycogen storage diseases (GSDs)**, specifically **von Gierke disease (GSD type I)**, which involves **glucose-6-phosphatase deficiency**. Glucagon stimulates glycogenolysis and gluconeogenesis, but **glucose-6-phosphatase** is essential for the final step of glucose release. Its absence in GSD I prevents glucagon from correcting hypoglycemia.
**Why the Correct Answer is Right**
**GSD type I (von Gierke disease)** is caused by **glucose-6-phosphatase deficiency**, blocking glucose release from glycogenolysis and gluconeogenesis. The liver becomes enlarged due to glycogen and lipid accumulation. **Glucagon** fails to correct hypoglycemia because it cannot bypass the missing enzyme. This is a **classic diagnostic clue** for GSD I.
**Why Each Wrong Option is Incorrect**
**Option A:** *GSD type II (Pompe disease)* involves **acid alpha-glucosidase deficiency**, leading to lysosomal glycogen accumulation. It presents with **cardiomegaly** and **hypotonia**, not massive hepatomegaly.
**Option B:** *GSD type III (Cori disease)* lacks **debranching enzyme