**Core Concept**
Pemphigus vulgaris is an autoimmune disease characterized by the formation of blisters on the skin and mucous membranes due to the breakdown of skin and mucosal tissues. The disease is caused by autoantibodies against desmoglein 3 proteins, which are essential components of hemidesmosomes that hold skin and mucosal cells together.

**Why the Correct Answer is Right**
In pemphigus vulgaris, the autoantibodies target desmoglein 3 proteins, leading to the disruption of cell-to-cell adhesion and the formation of intraepithelial blisters. This is because desmoglein 3 proteins play a crucial role in maintaining the integrity of skin and mucosal tissues by forming complexes with other proteins to hold cells together. The breakdown of these complexes results in the separation of cells and the formation of blisters.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because pemphigus vulgaris is not primarily caused by an abnormality in the basement membrane zone.
* **Option B:** This is incorrect because pemphigoid is a different autoimmune disease characterized by the formation of blisters due to autoantibodies against the basement membrane zone, not desmoglein 3 proteins.
* **Option C:** This is incorrect because epidermolysis bullosa is a group of genetic disorders characterized by the formation of blisters due to mutations in genes encoding proteins involved in skin cell adhesion, not autoantibodies against desmoglein 3 proteins.

**Clinical Pearl / High-Yield Fact**
The Nikolsky's sign, which is a characteristic feature of pemphigus vulgaris, can be elicited by gently rubbing a blistered area with a finger. This sign is due to the fact that the blisters in pemphigus vulgaris are intraepithelial, meaning they occur within the epidermis, and are therefore easily disrupted by gentle pressure.

**Correct Answer:** D