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The eczematous reaction pattern encompasses a wide variety of primary and associated secondary lesions. Eczema may be classified morphologically according to its chronicity. Table 8.1 lists the morphologic findings of acute, subacute, and chronic eczema. Acute eczema involves the constellation of vesicles and/or bullae, erythematous macules and/or plaques, oozing, and crusting (Figure 8.1). Early erosions may be seen. Subacute eczema is defined by the presence of scaly erythematous papules and/or plaques, along with round erosions and/or round crusts (Figure 8.2A,B). In chronic eczema there are scaly, lichenified plaques that may be hyper- and/or hypopigmented (Figure 8.3). Lichenification connotes thickened skin with increased skin markings and this finding occurs secondary to scratching and rubbing.

TABLE 8.1.Variants of Eczema by Chronicity and Their Morphologic Findings

Acute eczema with multiple vesicles that have coalesced to form a bulla, central crusting, and surrounding erythema.


(A) Subacute eczema showing widespread scaly plaques with small round erosions and crusts; (B) a close-up of subacute eczema showing the diagnostic small round erosions and crusts.


Chronic eczema, displaying lichenification, scaling, and pigmentary changes.

With the eczematous reaction pattern, we encounter, for the first time, a reaction pattern that comprises a single disease entity (albeit one with a wide variety of causes). From Table 8.1, and as discussed in Chapter 5, we see that, morphologically, there is significant overlap between acute eczema and the vesicobullous reaction pattern on one hand and chronic eczema and the papulosquamous reaction on the other. In fact, acute eczema may be classified with vesicobullous disease, and chronic eczema, with papulosquamous disease. Subacute ezema may also be categorized as a vesicobullous reaction pattern as the presence of round erosions infers preceding vesicles. It may additionally be classified as a papulosquamous reaction pattern if scaly plaques are the predominating clinical feature. It can therefore be argued that the eczematous reaction pattern can be folded completely into these two reaction patterns. The argument for keeping eczema as a separate reaction pattern rests on the fact that eczema is so commonly encountered that it is worthwhile to think about it separately. An additional reaction pattern that eczema can overlap with is the dermal reaction pattern. The earliest presentation of an acute contact dermatitis may be an edematous, erythematous plaque (Figure 8.4). This ...

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