Vesiculobullous Diseases

Intercellular 'fishnet' IgG. Pemphigus shows intercellular (fishnet) IgG deposition.

Subepithelial. Pemphigoid blisters are subepithelial with linear IgG at the BMZ.

Erythema multiforme. Target lesions typify erythema multiforme.

⭐ High-Yield Facts for Exam

Pemphigus vulgaris — intraepithelial split (acantholysis), Tzanck cells, fishnet/intercellular IgG on DIF; positive Nikolsky sign; potentially fatal.
Mucous membrane / bullous pemphigoid — subepithelial split, linear IgG/C3 at the basement membrane on DIF.
Erythema multiforme — acute hypersensitivity with target/iris lesions; Stevens-Johnson syndrome is a severe form.

Biopsy with histology + direct immunofluorescence (DIF) distinguishes these entities.

Pemphigus = intraepithelial + Tzanck + fishnet IgG; pemphigoid = subepithelial + linear IgG; EM = target lesions.

Q1. Pemphigus vulgaris shows which DIF pattern?

A. Linear at BMZ

B. Intercellular 'fishnet' IgG

C. Granular

D. Negative

Show Answer

✅ Answer: B

Pemphigus shows intercellular (fishnet) IgG deposition.

Q2. The level of blistering in pemphigoid is:

A. Intraepithelial

B. Subepithelial

C. Subcutaneous

D. Intradermal only

Show Answer

✅ Answer: B

Pemphigoid blisters are subepithelial with linear IgG at the BMZ.

Q3. Target (iris) lesions are characteristic of:

A. Pemphigus

B. Erythema multiforme

C. Lichen planus

D. Pemphigoid

Show Answer

✅ Answer: B

Target lesions typify erythema multiforme.

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