**Core Concept**
Pompe's disease is a rare, inherited disorder caused by deficiency of the enzyme acid alpha-glucosidase (GAA), leading to accumulation of glycogen in cells. This glycogen accumulation affects various organs and tissues.

**Why the Correct Answer is Right**
Hyperglycemia is not a characteristic feature of Pompe's disease. The disease is caused by glycogen accumulation in cells, but it does not lead to an increase in blood glucose levels. Instead, Pompe's disease is associated with hypoglycemia due to impaired glycogenolysis and gluconeogenesis. The enzyme deficiency affects the breakdown of glycogen to glucose, leading to decreased glucose levels in the blood.

**Why Each Wrong Option is Incorrect**
**Option B:** Cardiomyopathy is a feature of Pompe's disease, as the glycogen accumulation affects the heart muscle, leading to hypertrophy and fibrosis.
**Option C:** Skeletal myopathy is also a feature of Pompe's disease, as the glycogen accumulation affects the skeletal muscle, leading to muscle weakness and wasting.
**Option D:** Hepatomegaly is a feature of Pompe's disease, as the glycogen accumulation affects the liver, leading to liver enlargement.

**Clinical Pearl / High-Yield Fact**
Pompe's disease is an autosomal recessive disorder, and early diagnosis is crucial for management and treatment. A high index of suspicion is required for diagnosis, especially in infants and children with unexplained cardiomegaly or muscle weakness.

**Correct Answer:** **✓ Correct Answer: A. Hyperglycemia**