Bullous Disorders

Pemphigus Vulgaris

Key features

•    Intraepidermal blisters (suprabasal split)

•    Flaccid blisters, rupture easily → erosions

•    Almost always involves mucous membranes (oral ulcers common)

•    + Nikolsky’s sign: skin shears off with lateral pressure

Immunopathology

•    Autoantibodies (IgG) against desmoglein 3 (and sometimes desmoglein 1)

•    Immunofluorescence: "fish-net" or "chicken-wire" intercellular IgG staining

Epidemiology

•    Middle-aged, slightly more common in Mediterranean or Jewish ancestry

Treatment

•    High-dose systemic corticosteroids

•    Immunosuppressants (azathioprine, mycophenolate mofetil)

•    Rituximab for refractory cases

Bullous Pemphigoid

Key features

•    Elderly patients (>70 years)

•    Subepidermal blister → tense bullae that do not rupture easily

•    Less frequent mucosal involvement

Immunopathology

•    Autoantibodies against hemidesmosomal proteins (BP180, BP230)

•    Immunofluorescence: linear IgG and C3 along basement membrane

Clinical clues

•    Pruritus often precedes bullae

•    Can be triggered by furosemide, antibiotics (e.g., penicillamine)

Treatment

•    High-potency topical steroids (e.g., clobetasol)

•    Systemic steroids or immunosuppressants in widespread disease

Dermatitis Herpetiformis

Key features

•    Intensely pruritic, grouped vesicles and papules

•    Predominantly on extensor surfaces (elbows, knees, buttocks, scalp)

Associations

•    Coeliac disease (gluten-sensitive enteropathy)

•    HLA-DQ2, HLA-DQ8 positivity

Immunopathology

•    IgA deposits in dermal papillae on direct immunofluorescence

•    Granular IgA pattern

Treatment

•    Gluten-free diet (long-term resolution)

•    Dapsone (rapid symptomatic relief)

Other Bullous Conditions

Linear IgA Disease

•    Subepidermal blisters with linear IgA deposition at basement membrane

•    Can be idiopathic or drug-induced (e.g., vancomycin)

•    Similar clinical appearance to bullous pemphigoid

Epidermolysis Bullosa

•    Inherited mechanobullous disorders

•    Fragile skin, blistering with minor trauma

•    Subtypes (simplex, junctional, dystrophic) depend on level of split

Porphyria Cutanea Tarda (PCT)

•    Blisters on sun-exposed areas (e.g., hands, forearms)

•    Associated with liver disease, alcohol, hepatitis C, iron overload

•    Urine: pink under Wood’s lamp (porphyrins)

•    Treatment: phlebotomy, low-dose hydroxychloroquine

Extra Revision Pearls

•    Nikolsky’s sign:

o    Positive in pemphigus vulgaris, SJS/TEN

o    Negative in bullous pemphigoid

•    BP180 and BP230 → "Bullous Pemphigoid"

•    IgA in dermal papillae → pathognomonic for dermatitis herpetiformis

•    Always screen for coeliac disease in dermatitis herpetiformis