Feature	Pemphigus Vulgaris	Bullous Pemphigoid	Dermatitis Herpetiformis
Age of Onset	40-60	>60	20-40
Clinical Features	Painful Flaccid bullae → erosions Mucosal involvement common	Pruritic Tense bullae Mucosal involvement rare	Intensely pruritic Grouped vesicles Elbows, knees, buttocks affected
Histology	Intraepidermal cleavage	Subepidermal cleavage	Subepidermal cleavage with neutrophilic microabscesses
Immunofluorescence	Net-like intercellular IgG against desmosomes	Linear IgG against hemidesmosomes along basement membrane	Granular IgA deposits in dermal papillae

Bullous pemphigoid

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Etiology

• Type II hypersensitivity reaction
• Antihemidesmosome antibodies (IgG)

Clinical findings

• Large, tense, subepidermal blisters on normal, erythematous, or erosive skin
• Intensely pruritic lesions, possibly hemorrhagic, heal without scar formation
• Distributed on palms, soles, lower legs, groin, and axillae
• Oral involvement is rare

Diagnostics

• Tzanck test, Nikolsky sign: negative
• Histology and immunohistochemistry
  • Subepidermal vesicle formation
  • Eosinophil-rich infiltrate in underlying dermis
  • Immunofluorescence: deposition of linear IgG and C3 along the dermo-epidermal junction

Prognosis

• Benign disease, usually responds well to treatment
  • Blisters are deeper and more robust

Pemphigus vulgaris

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Etiology

• Type II hypersensitivity reaction
• IgG antibodies directed against desmoglein 3 and desmoglein 1 in desmosome

Clinical findings

• Progression in stages
  • Spontaneous onset of painful flaccid, intraepidermal blisters
  • Lesions rupture and become confluent → erosions and crusts → re-epithelialization with hyperpigmentation but without scarring
• Pruritus is typically absent.
• Lesions typically first present on the oral mucosa (> 50% of cases), then on body parts exposed to pressure (e.g., intertriginous areas)

Diagnostics

• Autoantibodies against
  • Desmoglein 3 and desmoglein 1
• Tzanck test, Nikolsky sign: positive
• Histology and immunohistochemistry
  • Intraepidermal vesicle formation just above the basal layer of the epidermis
  • Acantholysis on biopsy: loss of intercellular connections between keratinocytes (“row of tombstones” appearance)
  • Deposition of IgG in the intercellular spaces of the epidermis (esp. early lesions)
  • Immunofluorescence: deposition of IgG in a reticular pattern around epidermal cells

Prognosis

• Often fatal without treatment!
  • Caused primarily by infections, fluid loss, and electrolyte disturbances
    • Fragile blisters rupture easily