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The diagnosis of vesicular and bullous diseases in childhood can be a difficult task. To better understand the defining characteristics of vesiculobullous disorders, a general knowledge of skin anatomy is helpful. Figure 59-1 illustrates normal skin histology. The numerous causes of blistering can be divided into those with neonatal versus childhood onsets. Additionally, secondary characteristics, such as distribution and morphology, can further limit the differential diagnosis.

FIGURE 59-1.

Normal skin histology.

It is important to have a clear understanding of the terminology used to describe vesicular or bullous lesions and their associated physical features. A vesicle is a fluid-filled, dome-shaped lesion of 0.5 cm or less; if such a lesion is greater than 0.5 cm, it is termed a bulla. The fluid inside may be clear or hemorrhagic in nature. If the material is purulent, the lesion is called a pustule. Secondary lesions, including crusting, excoriation, scaling, milia, and scarring, may also be noted. An erosion is a superficially denuded vesicle with damage confined to the epidermis. Ulceration is a deeper lesion, with loss of the entire depth of the epidermis. Secondary scarring does not usually result from erosion, except if secondary infection occurs, but is common with ulceration given the depth of the injury (Table 59-1; Figure 59-2). Milia (small, white, superficial epidermal cysts) may result from a healing blistering process.

TABLE 59-1Definition of Vesiculobullous Lesions: Primary and Secondary Findings
FIGURE 59-2.

Clinical examples. A. Vesicle (scabies). B. Bulla (adverse reaction to topical cantharidin). C. Pustules (transient neonatal pustular melanosis). D. Erosion (eczema herpeticum). E. Ulcer (ulcerated infantile hemangioma).

Whether the vesicle or bulla is flaccid or tense, is another defining characteristic. A tense bulla suggests a deeper process in which the split in the epidermis lies below the level of the lamina lucida located in the basement membrane zone. This gives the lesion enough support to hold the fluid tense under pressure. In contrast, a flaccid bulla is ...

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