Correct Answer: D. Pemphigus vulgaris
Pemphigus vulgaris is the most common form of pemphigus in India and presents with flaccid bullae that rupture easily, leaving painful erosions. The pathognomonic histological finding is suprabasal acantholysis — loss of cell-to-cell adhesion (desmosomes) just above the basal layer, creating a characteristic "tombstone" appearance of basal cells. This suprabasal split distinguishes PV from other pemphigus variants. The disease is mediated by IgG autoantibodies against desmoglein 3 (mucosal) and desmoglein 1 (cutaneous), explaining the involvement of both oral mucosa and skin. Oral involvement (painful erosions, difficulty eating) is a hallmark feature in Indian patients and often precedes skin lesions. The flaccid nature of bullae reflects the intraepidermal location of the split, making them fragile and prone to rupture. Nikolsky sign is positive. Direct immunofluorescence shows intercellular IgG deposition in a "chicken-wire" pattern. This is the classic presentation taught in Indian dermatology curricula and is the most frequently tested pemphigus variant in NEET PG.
Why the other options are wrong
A. Pemphigus vegetans — Pemphigus vegetans is a benign variant of pemphigus vulgaris with suprabasal acantholysis, but it presents with vegetating lesions (hypertrophic, verrucous plaques) in intertriginous areas, not flaccid bullae. The clinical presentation is distinctly different — lesions are chronic, less painful, and lack the easy rupture characteristic of PV. This is a trap for students who know PV has suprabasal split but confuse the clinical morphology. B. Pemphigus foliaceus — Pemphigus foliaceus presents with flaccid bullae, but the split is subcorneal (within the stratum corneum), not suprabasal. This distinction is critical — PF typically spares oral mucosa and presents with superficial, crusted lesions on face and chest. The biopsy finding of suprabasal acantholysis directly excludes PF. NBE often pairs these two to test understanding of the histological level of split. C. Erythema multiforme — Erythema multiforme is a non-acantholytic condition with subepidermal blistering and a lymphocytic infiltrate at the dermoepidermal junction, not intraepidermal acantholysis. EM presents with targetoid lesions and is triggered by infections (HSV) or drugs, not autoimmune. The suprabasal split finding completely excludes EM. This option tests whether students confuse bullous diseases based on clinical appearance alone.
High-Yield Facts
- Suprabasal acantholysis is the pathognomonic histological finding in pemphigus vulgaris, distinguishing it from subcorneal split in pemphigus foliaceus.
- Desmoglein 3 and 1 antibodies cause PV; anti-Dsg3 alone causes mucosal-dominant disease, while anti-Dsg3 + anti-Dsg1 causes mucocutaneous involvement.
- Oral involvement (painful erosions, difficulty eating) is the presenting feature in 50–70% of Indian PV patients and often precedes skin lesions by weeks.
- Flaccid bullae that rupture easily are characteristic of intraepidermal blistering; tense bullae suggest subepidermal disease (bullous pemphigoid).
- Positive Nikolsky sign (intraepidermal) and chicken-wire IgG pattern on direct immunofluorescence confirm the diagnosis.
- Topical + systemic corticosteroids are first-line; steroid-sparing agents (azathioprine, mycophenolate) are used in India for long-term control.
Mnemonics
PV vs PF — Level of Split PV = Pemphigus Vulgaris = Vertical split (suprabasal); PF = Pemphigus Foliaceus = Follicular/Flaky (subcorneal). Remember: PV is deeper, PF is superficial. Desmoglein Antibodies in PV Dsg3 alone = mucosal-dominant (oral erosions only); Dsg3 + Dsg1 = mucocutaneous (oral + skin). Think: "3 = mouth, 1 = everywhere."
NBE Trap
NBE pairs pemphigus vulgaris and pemphigus vegetans to trap students who know both have suprabasal acantholysis but confuse the clinical morphology — vegetans presents with verrucous plaques, not flaccid bullae. The question tests whether students link histology to clinical presentation, not just memorize the split level.
Clinical Pearl
In Indian outpatient practice, a patient presenting with painful oral erosions and difficulty eating, followed weeks later by flaccid skin bullae, is pemphigus vulgaris until proven otherwise. Early oral involvement is the clinical pearl that should trigger immediate immunofluorescence testing and systemic corticosteroid therapy to prevent severe mucosal scarring and nutritional compromise.
_Reference: Robbins Ch. 25 (Skin); Harrison Ch. 52 (Bullous Diseases); OP Ghai Dermatology (Pemphigus section)_