Utility of epithelial membrane antigen immunostaining in the differentiation between palmoplantar pustulosis and pompholyx

摘要

Editor Palmoplantar pustulosis (PPP) and pompholyx commonly present as palmoplantar vesicles or pustules. These diseases share similar clinical and histological feature, and therefore, the differential diagnosis can be quite frustrating. The origin of pustules in PPP and vesicles in pompholyx were studied in some previous reports. In the PPP, the acrosyringium is suggested as the major site of vesicle/pustule formation. Pompholyx was originally hypothesized that dyshidrotic eczema by sweat gland dysfunction, but this has been disputed because vesicles are rarely associated with sweat ducts. Epithelial membrane antigen (EMA) is expressed by epithelial-origin cells included acrosyringeal cells, but not by normal keratinocytes. Therefore, we selected EMA to determine whether distinctive patterns exist in PPP and pompholyx lesions in relationship to the acrosyringium. Skin tissues were taken from 31 patients and grouped into 12 PPP and 19 pompholyx based clinicopathological diagnosis. For each sample, the immunohistochemical (IHC) staining in the keratinocytes was recorded as 0-2+. The results were summarized in Table 1. In PPP tissues, EMA staining was strongly localized in the pustular wall but focal or almost none in the surrounding keratinocytes (Fig. 1a), and eight of 12 samples demonstrated a direct connection between dermal eccrine ducts or acrosyringium with the vesicle. However in pompholyx, it was expressed diffusely in most regional keratinocytes and especially more strongly near the eccrine ducts (Fig. 1b). The vesicular wall also expressed EMA, and interestingly, there was a tendency for larger vesicles to stain more readily than smaller ones (Fig. 1c). Meanwhile, PPP presented with one or two micropustules with a flask or wine glass shape, but pompholyx had multilocular form vesicles (Fig. 1a,b).