Fig. 41.1
Left upper panel shows a middle-aged woman with generalized painful erosions of pemphigus vulgaris. Right upper panel shows an old man with generalized bullous pemphigoid. Right lower panel shows an older woman with inflammatory epidermolysis bullosa acquisita. Note the similarity of lesions to bullous pemphigoid. Left lower panel shows a 10-year-old boy with pemphigus herpetiformis. Note shallow erosions. Multiple biopsies showed eosinophilic spongiosis and immunofluorescence showed IgG around epidermal cells
Introduction
Many skin disorders may have blisters. In some, the blisters are secondary and occur occasionally or rarely. Examples include lichen planus (LP) and erythema multiforme (EM). These disorders are generally nonblistering; but in a few patients, some of the lesions may develop blisters due to severe degeneration of the basal layer. These disorders will not be discussed here as each disorder usually retains its characteristic features in other lesions, so clinical recognition is generally easy.
Some common infections result in blisters. These include viruses, such as herpes simplex virus, varicella-zoster virus, and Coxsackie virus; bacteria, such as Staphylococcus aureus, superficial fungi, and Candida. The clinical characteristics in these disorders usually suffice to make an accurate clinical diagnosis. In some cases, cultures may be indicated. These disorders will also not be discussed.
Sometimes blisters arise due to epidermal necrosis. This occurs in many skin disorders whose primary clinical presentation is sloughing. These include physical factors, such as severe sunburn, extreme heat or extreme cold, and acute radiation; chemical factors, such as exposure to acid or alkali; and reaction to medication, such as Steven–Johnson Syndrome (SJS) and toxic epidermal necrolysis (TEN) . Again, these disorders will not be discussed here (discussed in Chap. 33).
Instead, this section addresses disorders that reveal blisters as the primary lesion and are referred to as primary bullous disorders. Many are autoimmune in pathogenesis.
Classification
There is more than one approach to the diagnosis of a bullous disorder. The following approach takes into consideration distribution of lesions, predominant morphology, and possible inducing factors.
I.
Generalized predominantly intact blisters
BP, EBA, LAD, DH, SLE
II.
Generalized, with extensive erosions
PV, PF, PNP
III.
Limited to the legs
Edema, diabetes mellitus (DM), pretibial epidermolysis bullosa (EB), localized bullous pemphigoid (BP)
IV.
Localized trauma-induced
PCT, pseudo-PCT, EBA
Generalized with Predominantly Intact Blisters
BP, EBA, LAD, DH, SLE
Clinical Clues
This group consists of five autoimmune disorders, all of which are subepidermal (BP, epidermolysis bullosa acquisita (EBA II), linear IgA disease (LAD), dermatitis herpetiformis (DH), and the bullous eruption of systemic lupus erythematosus (SLE)).
Some clinical features may favor one disorder over the others. For example, predominant involvement over the joints and extensor surfaces, especially if lesions are small, strongly favors DH. In at least two-thirds of the patients with BP, lesions strongly favor skin folds, especially the inner thighs. EBA II mimics BP strongly; unlike EBA type I in which lesions are generally trauma induced and frequently heal with milia, lesions in EBA II are surrounded by inflammation, just as in BP.
LAD may also mimic BP to a large degree except in hospitalized patients, where it presents more acutely and secondary to a drug, such as vancomycin. The bullous eruption of SLE occurs in patients usually known to have SLE. Lesions are often scattered randomly without favoring photodistributed areas or having a characteristic pattern. Many blisters often arise within urticarial plaques. Except for classic DH and classic BP, histological and immunofluorescence examination is absolutely necessary.
Histological Clues
The ideal specimen for histological evaluation of a blistering eruption is a shave biopsy specimen that includes a vesicle with surrounding intact skin. The border of the vesicle often reveals the earliest changes that result in blistering, and that are important in making a diagnosis.
All the above disorders reveal a subepidermal blister with an underlying superficial dermal infiltrate that may also be seen in the overlying epidermis and in the blister cavity. The infiltrate is predominantly or exclusively neutrophilic in all except BP, in which the infiltrate is predominantly or exclusively eosinophilic. In general, neutrophil-predominant infiltrates in the skin tend to contain some eosinophils and eosinophil predominant infiltrates tend to contain some neutrophils.
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