Immunobullous Disorders Flashcards
Name three immunobullous disorders
- pemphigus vulgaris
- bullous pemphigoid
- dermatitis herpetiformis
Describe the aetiology of pemphigus vulgaris
Rare autoimmune disease IgG auto-antibodies are made against desmoglein 1/3 the protein in desmosomes which attach cells in the prickle cell layer.
What happens in pemphigus vulgaris when immune complexes form on the cell surface
Complement activation and protease release leads to acantholysis where keratinocytes separate from each other, producing fluid filled blisters
Where does pemphigus vulgaris typically affect?
Scalp, face, axillae, groin
How does pemphigus vulgaris present?
Flaccid vesicles/bullae that rupture to leave a raw area - mucosal involvement is common
What sign is positive in pemphigus vulgaris?
Nikolsky sign - top layers of the skin slip away from the lower layers when rubbed - suggest a cleavage in the epidermis
What would immunofluoresence show in pemphigus vulgaris?
Cell surface bound IgG net-like pattern in epidermis
How is pemphigus vulgaris treated?
Systemic therapy - high does weaning course of oral steroids in combination with an immunosuppressant
Describe the pathology of bullous pemphigoid
Circulating IgG reacts with antigens of the hemidesmosomes at the DEJ leading to complement activation and tissue damage - leading to cleavage of skin at DEJ leading to sub epidermal blisters
How does bullous pemphigoid typically present
Large bull on erythamtous base, blister to leave erosions, may be localised to one area or widespread on trunk and limbs. Presents will itchy plaques and papules.
Who is often affected by bullous pemphigoid?
Elderly people
What is the aetiology of bullous pemphigoid?
IgG autoantibodies to basement membrane antigens
What will bullous pemphigoid look like on immunofluorescent labelling?
Linear IgG at basement membrane
Is bullous pemphigoid Nikolsky positive or negative?
Negative
How is Bullous pemphigoid managed?
Localised disease - topical super potent steroids
Widespread - Oral steroids and immunosuppressant/tetracyline and nicotinamide
Describe the aetiology of dermatitis herpetiformis
IgA auto-antibodies to gluten tissue trans-glutaminase in the gut and epidermis. IgA targets gliadin in gluten but cross reacts with connective tissue matrix proteins
What happen in dermatitis herpetiformis when immune complexes form?
Activation of complement and neutrophil chemotaxis leads to intensely itchy lesion & papillary dermal micro abscesses
What disease do 75% of patients with dermatitis herpetiformis have?
Coeliac disease
How will dermatitis herpetiformis present?
Itchy vesicles or small blisters usually on extensors and bum.
How will dermatitis herpetiformis appear on immunofluorescence?
Granular IgA in dermal papillary tips
What is the treatment for dermatitis herpetiformis?
Gluten free diet & oral dapsone (antibiotic thought to inhibit neutrophil migration)
