Learning Objective
By the end of this lesson, the learner should be able to describe the pathogenesis, clinical presentation, histopathology, immunofluorescence patterns, and management of major vesicular and bullous skin disorders.
Activity
Pemphigus
Type: Rare, potentially fatal autoimmune disorder.
Pathogenesis: Autoantibodies against desmoglein 3 → loss of keratinocyte adhesion (acantholysis) → intraepidermal blisters.
Clinical Features: Flaccid blisters, easily ruptured; oral/mucosal involvement is common.
Microscopy: Intraepidermal acantholysis; basal keratinocytes form a tombstone pattern.
Immunofluorescence: Net-like IgG deposits between keratinocytes.
Treatment: Immunosuppression.
Bullous Pemphigoid
Type: Common autoimmune disease in older adults.
Pathogenesis: Autoantibodies against hemidesmosomal BP180/BP230 → subepidermal blisters.
Clinical Features: Tense bullae resistant to rupture.
Immunofluorescence: Linear IgG deposits at the dermal-epidermal junction.
Treatment: Immunosuppression; generally milder than pemphigus.
Dermatitis Herpetiformis
Association: Strongly linked to celiac disease.
Pathogenesis: IgA antibodies → granular IgA deposits at dermal papillae tips → subepidermal blisters.
Clinical Features: Intensely pruritic grouped vesicles/bullae on extensor surfaces.
Microscopy: Microabscesses in dermal papillae → subepidermal separation.
Treatment: Gluten-free diet ± immunosuppressants.
Porphyria Cutanea Tarda
Type: Disorder of heme synthesis (acquired or familial).
Clinical Features: Blistering on sun-exposed areas, triggered by trauma or UV.
Microscopy: Subepidermal blisters with minimal inflammation, thickened dermal vessels.
Immunofluorescence: Ig and complement deposition at the basement membrane and around dermal vessels.
Management: Sun protection, phlebotomy, and treating underlying liver disease.
Erythema Multiforme
Type: Hypersensitivity reaction to infections (HSV, Mycoplasma) or drugs (sulfonamides, penicillin, phenytoin).
Clinical Features: Targetoid lesions, vesicles, and bullae.
Severe Form: Stevens-Johnson syndrome – extensive skin and mucous membrane involvement.
Treatment: Supportive; remove offending agent or treat infection.
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