## **Core Concept**
The question tests knowledge on disorders of carbohydrate metabolism, specifically focusing on the association with cardiac involvement. Disorders of carbohydrate metabolism include glycogen storage diseases, which are a group of conditions characterized by defects in enzymes involved in glycogen synthesis or breakdown. These disorders can affect various organs, including the liver, muscles, and heart.

## **Why the Correct Answer is Right**
The correct answer, **Pompe disease (Glycogen storage disease type II)**, is associated with cardiac involvement due to the accumulation of glycogen in lysosomes of cardiac and skeletal muscle cells. This accumulation occurs because of a deficiency in acid alpha-glucosidase (acid maltase), the enzyme responsible for breaking down glycogen within lysosomes. The accumulation of glycogen leads to cellular dysfunction and damage, particularly in the heart, resulting in cardiomegaly and heart failure.

## **Why Each Wrong Option is Incorrect**
- **Option A: Glycogen storage disease type I (Von Gierke disease)** primarily affects the liver and is characterized by a deficiency in glucose-6-phosphatase. While it leads to severe hypoglycemia, lactic acidosis, and hepatomegaly, cardiac involvement is not a typical feature.
- **Option B: Glycogen storage disease type III (Cori disease)** involves a deficiency in the debranching enzyme and affects the liver and muscles. It can lead to cirrhosis and progressive liver disease but is less commonly associated with primary cardiac involvement compared to Pompe disease.
- **Option C: Glycogen storage disease type IV (Andersen disease)** results from a deficiency in the branching enzyme and primarily affects the liver, leading to progressive cirrhosis. Cardiac involvement is not a hallmark of this disease.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Pompe disease is one of the few glycogen storage diseases with significant cardiac involvement, presenting with cardiomegaly and often leading to heart failure. Early diagnosis and treatment, including enzyme replacement therapy, are crucial for improving outcomes.

## **Correct Answer: D. Pompe disease.**