A patient presents with itchy skin lesions with blistering along with gastrointestinal issues. Which of the following is the most specific serological test for this condition?

IgA deposits at the dermoepidermal junction

Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.

Statements 1 & 2 are correct, 2 is not explaining 1

Statements 1 and 2 are correct and 2 is the correct explanation for 1

Statements 1 and 2 are incorrect

A 74-year-old woman has noted increasing size and number of darker brown patches on the dorsum of each hand for the past 15 years. They do not change with sun exposure, are nonpruritic, and non-tender. On examination, these 0.5- to 1-cm lightly pigmented lesions are flat. Which of the following is the most likely microscopic finding in these lesions?

Loss of melanin in surrounding skin

Which of the following is NOT true about dysplastic nevus syndrome?

It is inherited in an autosomal recessive pattern.

Approximately half of such patients develop melanoma by age 60.

It is associated with mutations in BRAF and NRAS.

It is a disorder characterized by numerous dysplastic nevi.

Blistering Diseases for NEET-PG: High-Yield Pathology Lessons

Blistering Basics - Bubble Trouble Intro

Blister: Localized fluid collection within or below the epidermis.
- Vesicle: < 1 cm diameter.
- Bulla: > 1 cm diameter.
Anatomical Levels of Cleavage (key to classification):
- Intraepidermal (within the epidermis):
  - Subcorneal: Beneath stratum corneum.
  - Intraspinous: Within stratum spinosum (acantholysis).
  - Suprabasal: Above basal cell layer.
- Subepidermal (at/below Dermo-Epidermal Junction - DEJ):
  - Lamina Lucida: Within upper basement membrane zone.
  - Lamina Densa: Within middle basement membrane zone.
  - Sub-Lamina Densa: Below lamina densa (anchoring fibril zone).

⭐ The level of split is the most crucial initial step in classifying blistering diseases.

Intraepidermal Blisters - Skin's Inner Strife

Mechanism: Acantholysis (loss of keratinocyte adhesion). Autoantibodies target Desmogleins.
Clinical: Flaccid blisters, Nikolsky sign positive (epidermal separation on pressure).
DIF: Intercellular 'chicken-wire' IgG & C3 deposits.
Key Types:
- Pemphigus Vulgaris (PV):
  - Targets: Dsg3 (mucosa/skin) ± Dsg1 (skin).
  - Clinical: Oral erosions (80-90%), flaccid skin blisters; deeper split.
- Pemphigus Foliaceus (PF):
  - Target: Dsg1 only (superficial epidermis).
  - Clinical: Scaly, crusted erosions; no mucosal involvement. Fogo Selvagem form.
- IgA Pemphigus: IgA deposits; neutrophilic pustules.
- Paraneoplastic Pemphigus: Malignancy-associated; severe stomatitis, polymorphic lesions.

📌 Mnemonic: Vulgaris = Very deep (Dsg3); Foliaceus = Flakes (superficial Dsg1).

⭐ Pemphigus vulgaris commonly affects oral mucosa (80-90%) and skin; Pemphigus foliaceus spares mucous membranes.

Subepidermal Blisters - Dermal Divide Drama

Mechanism: Immune attack on dermoepidermal junction (DEJ) structural components → separation below epidermis, forming tense blisters. 📌 'B'P = 'B'asement membrane, 'B'elow.
Key Diseases & Features:

Disease	Antigen(s)	DIF	Clinical
Bullous Pemphigoid (BP)	BPAG1 (BP230), BPAG2 (BP180)	Linear IgG/C3 at BMZ	Elderly, tense subepidermal bullae, intense pruritus, Nikolsky usually negative.
Dermatitis Herpetiformis (DH)	Epidermal/Tissue Transglutaminase (eTG/tTG)	Granular IgA in dermal papillae	Intensely pruritic grouped vesicles (extensors), strong celiac disease association.
Epidermolysis Bullosa Acquisita (EBA)	Type VII collagen	Linear IgG/C3 at BMZ (dermal side salt-split)	Trauma-induced non-inflammatory blisters, acral distribution, heals with scarring & milia.
Linear IgA Bullous Dermatosis (LABD)	LAD-1 (cleaved BPAG2), LABD97	Linear IgA at BMZ	Children/adults, annular or "string of pearls" vesicles/bullae.
Cicatricial Pemphigoid	BP180, Laminin-332, Type VII collagen	Linear IgG/C3/IgA at BMZ	Chronic, mainly mucosal (oral, ocular) blisters with progressive scarring.
Pemphigoid Gestationis	BP180 (BPAG2)	Linear C3 (± IgG) at BMZ	Pregnancy (2nd/3rd trimester)/postpartum, pruritic urticarial papules/plaques then blisters, often periumbilical.

DIF patterns in blistering diseases

Diagnostic Approach - Skin Sleuth Central

Key Investigations:
- Skin Biopsy: H&E (split level, infiltrate); DIF (perilesional, gold standard for immune deposits).
- IIF (Serum): Detects circulating autoantibodies (substrates: monkey esophagus, salt-split skin).
- ELISA: Quantifies specific autoantibodies (e.g., Dsg1, Dsg3, BP180, BP230).
- Tzanck Smear: Herpes (multinucleated giant cells); Pemphigus (acantholytic cells).
- Nikolsky Sign: Clinical indicator of epidermal fragility.
Diagnostic Flow:

![Diagnostic Algorithm for Blistering Diseases](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Pathology_Dermatopathology_Blistering_Diseases/2d7db5fc-96ee-4a4c-a728-a78b4bafb303.png)

⭐ Salt-split skin immunofluorescence is crucial: in Bullous Pemphigoid, antibodies bind to the roof (epidermal side) of the split, while in Epidermolysis Bullosa Acquisita, they bind to the floor (dermal side).

High‑Yield Points - ⚡ Biggest Takeaways

Pemphigus vulgaris: Intraepidermal bullae due to acantholysis; Nikolsky positive; targets Desmoglein 3 & 1.

Bullous pemphigoid: Subepidermal, tense blisters; Nikolsky negative; targets hemidesmosomal proteins (BPAG1/BPAG2).

Dermatitis herpetiformis: Subepidermal with neutrophilic papillary microabscesses; IgA deposits; strong celiac disease link.

Epidermolysis bullosa: Inherited mechanobullous disorders; blisters from minor trauma; variable cleavage planes.

Pemphigus foliaceus: More superficial intraepidermal (subcorneal) blisters; targets Desmoglein 1 primarily.

Linear IgA Bullous Dermatosis (LABD): Subepidermal blisters with linear IgA deposition along the basement membrane zone.

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