**Core Concept**
Stemmer's sign is a clinical indicator used to assess the severity of lymphedema. Lymphedema is a chronic condition characterized by swelling in the limbs due to the accumulation of protein-rich fluid. The presence of Stemmer's sign is a significant finding that often correlates with the advanced stages of lymphedema.

**Why the Correct Answer is Right**
Stemmer's sign is characterized by the inability to pinch a fold of skin on the dorsum of the foot due to the presence of subcutaneous fibrosis. This fibrosis occurs as a result of chronic inflammation and scarring in the affected limb. The fibrotic tissue binds the skin to underlying structures, making it difficult to create a skin fold. This is a specific and sensitive indicator of advanced lymphedema.

**Why Each Wrong Option is Incorrect**
**Option A:** Swelling in the foot seen with lymphoedema is a symptom of lymphedema, but it is not Stemmer's sign.
**Option B:** Loss of normal perimalleolar shape in lymphoedema is a feature of lymphedema, but it is not a specific indicator of its severity.
**Option D:** Pitting edema in filariasis is a symptom of filarial infection, but it is not related to Stemmer's sign.

**Clinical Pearl / High-Yield Fact**
Stemmer's sign is a crucial indicator of advanced lymphedema, often necessitating surgical intervention. It is essential for surgeons and clinicians to recognize this sign to provide timely and effective management.

**Correct Answer:**
✓ Correct Answer: C. Subcutaneous fibrosis which makes skin over dorsum of foot not pinchable