**Core Concept**
The patient's symptoms, particularly the presence of flaccid bullae and oral erosions, along with histopathological findings of intraepidermal acantholytic blisters, point towards a diagnosis of a skin disorder characterized by autoantibody-mediated cell destruction.

**Why the Correct Answer is Right**
The patient's presentation is consistent with Pemphigus Vulgaris (PV), a chronic autoimmune skin disease caused by autoantibodies against desmoglein 3 proteins, which are crucial components of desmosomes that hold epidermal cells together. The autoantibodies disrupt these cell-cell adhesions, leading to intraepidermal blister formation. The oral lesions are a hallmark of PV, often preceding the skin lesions. Histopathology confirms the diagnosis with the presence of acantholytic cells, which are keratinocytes that have lost their cell-cell adhesion.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) typically present with more widespread skin involvement, mucous membrane erosions, and a history of medication use within the past few days.

**Option B:** This option is incorrect because Bullous Pemphigoid (BP) is characterized by subepidermal blisters, whereas the patient's histopathology shows intraepidermal blisters.

**Option C:** This option is incorrect because Erythema Multiforme (EM) typically presents with target lesions on the skin and mucous membranes, but does not typically exhibit the same degree of blistering as seen in this patient.

**Option D:** This option is incorrect because Dermatitis Herpetiformis (DH) presents with intensely itchy, blistering skin lesions that are more commonly seen on the elbows, knees, and buttocks, and is associated with celiac disease.

**Clinical Pearl / High-Yield Fact**
Pemphigus Vulgaris often presents with oral lesions before skin lesions, and the histopathology is characterized by intraepidermal acantholytic blisters. It is essential to consider this diagnosis in patients with persistent oral erosions and flaccid bullae.

**Correct Answer: D. Bullous Pemphigoid**