Intraepidermal Vesicular and Pustular Diseases

The classification of vesicles and bullae are discussed in general in Section 1.147. Many of them are not discussed in this chapter. Some subepidermal diseases can appear to be intraepidermal when they have re-epithelialized. Intraepidermal diseases can also appear subepidermal if the blister blows out into the subepidermal zone or if there is prominent papillary dermal edema. The most common causes of intraepidermal vesicles are eczema (2.1) and contact dermatitis (2.2), but these diseases are in the chapter on eczematous diseases because they also commonly have that morphology. To diagnose an intraepidermal vesicular disorder, the pathologist pays particular attention to three things: (1) the site of the blister ( subcorneal , midepidermis , or suprabasal ); (2) the type of inflammatory cells involved ( neutrophils , lymphocytes , or eosinophils ); and (3) the mechanism of blister formation ( spongiosis [1.132], acantholysis [1.2], ballooning degeneration , or epidermolysis ). See 1.89 for other diseases with pustules in the epidermis (many are subcorneal).

5.1

Acropustulosis of infancy

(see Fig. 5.1 )

Uncommon idiopathic pustules on acral skin of infants is a diagnosis made only after other causes of pustules have been excluded. It usually resolves within 2 years.

• ■

  Subcorneal pustule of neutrophils

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  Perivascular (1.109) neutrophils and lymphocytes

Differential diagnosis

• 1.

  Other subcorneal pustules (1.89), especially scabies (15.9), impetigo (12.1), candidiasis (13.4), and tinea (13.1).