**Core Concept**
Glycogen storage diseases (GSDs) are a group of metabolic disorders caused by enzyme deficiencies that result in abnormal glycogen accumulation in various tissues, including muscles. These diseases are classified into different types based on the specific enzyme deficiency and the affected tissues. One of the key enzymes involved in glycogen metabolism is glycogen synthase, which is responsible for glycogen synthesis.

**Why the Correct Answer is Right**
The correct answer is a type of glycogen storage disease that primarily affects the liver and does not significantly impact muscle glycogen metabolism. This is because the enzyme deficiency in this disease type affects the liver's ability to synthesize glycogen, but it does not affect the muscle's ability to break down or synthesize glycogen.

**Why Each Wrong Option is Incorrect**
* **Option A:** Glycogen storage disease type IV (Andersen disease) affects both the liver and muscles due to a deficiency in the glycogen-branching enzyme, leading to abnormal glycogen accumulation in these tissues.
* **Option B:** Glycogen storage disease type III (Cori disease) affects both the liver and muscles due to a deficiency in the debranching enzyme, leading to abnormal glycogen accumulation in these tissues.
* **Option C:** Glycogen storage disease type VI (Hers disease) affects the liver and muscles due to a deficiency in the liver phosphorylase kinase enzyme, leading to abnormal glycogen accumulation in these tissues.

**Clinical Pearl / High-Yield Fact**
Glycogen storage diseases can be classified into two main categories: those that affect the liver (e.g., GSD type I, GSD type III, GSD type VI) and those that affect both the liver and muscles (e.g., GSD type IV, GSD type V). It's essential to understand the specific enzyme deficiencies and affected tissues for each type to diagnose and manage these diseases effectively.

**Correct Answer:** D.