**Core Concept**
Dyskeratosis is a histopathological feature characterized by premature keratinization of epidermal cells, leading to the formation of abnormal cells with hyperchromatic nuclei and a distinct cell membrane. This process is a hallmark of certain skin disorders, particularly those involving the keratinocyte layer.

**Why the Correct Answer is Right**
Darier's disease is a rare genetic disorder caused by mutations in the ATP2A2 gene, which encodes a calcium pump responsible for regulating intracellular calcium levels. The resulting abnormal calcium signaling disrupts keratinocyte differentiation, leading to the accumulation of abnormal keratin filaments and the characteristic dyskeratotic cells seen in Darier's disease. This process is a direct result of the disrupted calcium homeostasis, which affects the normal functioning of keratinocytes.

**Why Each Wrong Option is Incorrect**
**Option A:** Pemphigus vulgaris is an autoimmune disorder characterized by the formation of autoantibodies against desmoglein 3, leading to the breakdown of intercellular connections between keratinocytes. While pemphigus vulgaris does involve abnormal keratinocyte behavior, it does not typically exhibit dyskeratosis.

**Option B:** Bullous pemphigoid is another autoimmune disorder, but it primarily involves the formation of autoantibodies against components of the basement membrane zone, leading to the separation of the epidermis from the dermis. Dyskeratosis is not a characteristic feature of bullous pemphigoid.

**Option D:** Hailey-Hailey disease, also known as familial benign pemphigus, is a rare genetic disorder caused by mutations in the ATP2C1 gene, which encodes a calcium pump involved in the regulation of intracellular calcium levels. While it does share some similarities with Darier's disease, Hailey-Hailey disease primarily presents with blistering and erosions rather than dyskeratosis.

**Clinical Pearl / High-Yield Fact**
When differentiating between various skin disorders, remember that dyskeratosis is a hallmark of Darier's disease, but not typically seen in pemphigus vulgaris or bullous pemphigoid. Hailey-Hailey disease can present with some similar histopathological features, but it is primarily characterized by its blistering and erosive nature.

**✓ Correct Answer:** C. Darier's disease