An immune mediated blistering disease of elderly people, which often starts with urticaria-like and pruritic
erythematous lesions.
Later, large dense blisters develop in both erythematous and normal skin.
The bullae are subepidermal and intact epidermis forms the roof.
Auto-antibodies to the epidermal basement membrane zone (Figure 3)are found on direct immunofluorescence microscopy.
Etiology:
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Age of onset averages between 65 and 75.
No predominant HLA association.
Sex incidence is equal overall.
Bullous pemphigoid antigens are hemidesmosomal components, located below the basal epithelial cells.
Clinical Features
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Commonly starts with non-specific rashes on the limbs which may be either urticaria-like
or occasionally eczematous and rarely may simulate vesicular eczema.
If it is urticarial-like, prodrome lasts 1-3 weeks before blisters occur
If it is eczematous - the bullaes may not develop for several months.
Figurate erythema with large tense bullae(Figure 1) .The changes may closely resemble erythema
multiforme or dermatitis herpetiformis.
General eruption of pemphigoid follows the prodromal phase and most of the body may be affected within
a week.
Bullae may arise on erythematous or normal skin and may be
associated with subcutaneous edema.
The bullae are dense and dome-shaped,
the diameter are up to 7 cm, mainly on the flexural aspects of limbs and on central abdomen.
Mucosal lesions are usually confined to the mouth and they are less frequent and less severe than in pemphigus vulgaris.
The illness is usually accompanied by leukocytosis.
A few patients have reported exacerbation or precipitation of their disease by UV light.
Pathology:
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Tentative mechanism for the pathophysiology of blister formation is associated with antibodies that bind to basement membrane zone and activate complement.
The dermal infiltration contains mainly eosinophils, but can also contain neutrophils, lymphocytes and mononuclear cells.
Direct immunofluorescence : IgG (most are IgG1 and IgG4)(Figure 2)and C3, or C3 along the basement membrane zone. IgA or IgE can also be seen infrequently.
Indirect Immunofluorescence: Most patients have circulating IgG attack basement membrane zone of all stratified, squamous epithelium, gall bladder ,bladder , urethra ,trachea and bronchi.
Immuno-electron microscope:
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IgG deposit localized to hemidesmosomal and upper lamina lucida areas.
Treatment:
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Systemic corticosteroid
For patients with localized disease ,topical or intralesional steroids may be sufficient to control the disease. Tetracycline, Erythromycin, Niacinamide have been used successfully for localized disease.
Azathioprine can significantly reduce steroid requirement .
Recently it has been suggested that dapsone is considered as first line therapy.
Differential Diagnisis:
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Burns, staphylococcal scaled skin syndrome, psoriasis, leg ulcers and eczema, urticaria, pemphigus, EBA, impetigo, linear IgA bullous dermatitis.
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