White : Diseases of the Skin - Blistering Disorders

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Gary M. White & Neil H. Cox

Diseases of the Skin

16	Blistering Disorders

APPROACH TO BLISTERING ERUPTIONS

Classification, patterns, and causes of blistering

Blisters may be classified according to:

•	aetiology, for example immunobullous, mechanobullous, infective, or inflammatory (Table 16.1); and
•	pathologic features, such as the part of the skin where blister formation occurs (e.g. intraepidermal or subepidermal).

Each of these classifications has clinical relevance. It is important to interpret the clinical morphology, as this helps in identification of the level of blistering within the skin, which in turn narrows the diagnostic possibilities. For example, subepidermal blisters with a normal epidermis over the blister split are typically tense, unilocular blisters (e.g. bullous pemphigoid), intraepidermal blisters may present as crusts rather than intact blisters (e.g. pemphigus), and blisters with epidermal necrosis look gray even if they actually have clear fluid content (e.g. erythema multiforme). Associated clinical history such as duration, features such as inflammation, and investigations such as immunopathology all help to refine the diagnosis.

Investigation of blistering disorders

The investigation of blisters will, in general, fall into three categories.

•	History and examination—clinical history, family history, antecedent events including possible contact allergens, medications, pattern and morphology of the blisters and of any associated rash, mucous membrane involvement, etc.
•	Investigations to establish the cause or diagnosis—skin biopsy is usually the most important, but tests such as swabs for bacteriology or virology may be important if infection is suspected, and others such as antibodies for vasculitis, porphyrin levels, etc. may be dictated by the likely diagnosis in individual cases. To diagnose the immunobullous disorders, skin biopsies generally require some tissue to be frozen for direct immunofluorescence (see later). It is helpful to appreciate important structures in the skin of relevance to blistering disorders (Fig.16.1).
•	Investigations needed as a therapeutic baseline—especially for immunobullous disorders, where corticosteroids or immunosuppressive therapy may be required (check blood pressure, glucose, full blood count, and renal and hepatic function); see Chapter 4 for more detail.

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