**Core Concept**
Gottron's papules are a characteristic dermatological manifestation associated with dermatomyositis, a subtype of inflammatory myopathy. They are a type of skin lesion that occurs due to the deposition of immune complexes and the activation of T-cells in the skin, leading to inflammation and damage to the dermal-epidermal junction.

**Why the Correct Answer is Right**
Gottron's papules typically appear as erythematous to violaceous papules or plaques over the knuckles, elbows, and knees. They are thought to result from the activation of CD4+ T-cells and the release of pro-inflammatory cytokines, which contribute to the breakdown of the dermal-epidermal junction. The presence of Gottron's papules is a key diagnostic clue for dermatomyositis, which can be distinguished from other inflammatory myopathies by its distinctive skin and muscle manifestations.

**Why Each Wrong Option is Incorrect**
**Option A:** While Gottron's papules are indeed associated with dermatomyositis, they are not a hallmark feature of polymyositis, another subtype of inflammatory myopathy.
**Option B:** Erythema nodosum is a separate entity characterized by painful subcutaneous nodules, often associated with infections or inflammatory bowel disease, and is not directly related to Gottron's papules.
**Option C:** Vittiligo is an autoimmune condition characterized by the loss of melanocytes, leading to depigmented skin patches, and is not associated with Gottron's papules.

**Clinical Pearl / High-Yield Fact**
Gottron's papules are a key differentiator between dermatomyositis and polymyositis, and their presence should prompt further investigation into the patient's muscle strength and function.

**Correct Answer: C. Vittiligo.**