**Core Concept**
The presence of histiocytes with PAS positive cytoplasm in a one-year-old boy with hepatosplenomegaly and delayed milestones suggests a storage disorder involving lysosomal enzymes. This condition is characterized by the accumulation of carbohydrates in histiocytes due to a deficiency of the enzyme responsible for their breakdown.

**Why the Correct Answer is Right**
The histiocytes with PAS positive cytoplasm are likely to be Gaucher cells, which are characteristic of Gaucher disease. Gaucher disease is caused by a deficiency of the enzyme glucocerebrosidase, leading to the accumulation of glucocerebroside in histiocytes. Electron microscopic examination of these histiocytes would reveal the presence of myelin figures and lipid inclusions, which are characteristic of Gaucher cells. The myelin figures are formed due to the membrane-bound lipid inclusions, and they are visible under an electron microscope.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the clinical presentation and histopathological findings described.
**Option B:** This option does not relate to the storage disorder involving carbohydrates in histiocytes.
**Option C:** This option is not a characteristic feature of the histiocytes in Gaucher disease.

**Clinical Pearl / High-Yield Fact**
Gaucher disease is an autosomal recessive disorder, and it is the most common lysosomal storage disorder. It is characterized by the accumulation of glucocerebroside in histiocytes, leading to hepatosplenomegaly, anemia, and bone marrow failure.

**Correct Answer: C. Myelin figures and lipid inclusions.**