Erosive Pustular Dermatosis of the Scalp: A Clinicopathologic Study of Fifty Cases.

Erosive pustular dermatosis of the scalp (EPDS) is an uncommon, pustular, idiopathic disorder typically occurring on the scalp of the elderly, whose diagnosis requires close clinicopathologic correlations. Recently, the primary histopathologic characteristic of EPDS has been identified in some biopsies from hair-bearing scalp lesions as a sterile, vesiculo-pustule involving the infundibulum of hair follicles. To further delineate the clinicopathologic spectrum of the disease, we led a retrospective study of 50 patients (36 males and 14 females) with a diagnosis of EPDS between 2011 and 2021, reviewing clinical and histopathological data. Androgenetic alopecia was present in 32 patients. Triggering factors were present in 21 patients. The vertex was the most common location; one patient also had leg involvement. Two cases were familial. Disease presentation varied markedly from tiny, erosive, scaly lesions to crusted and hemorrhagic plaques, mimicking pustular pyoderma gangrenosum (PPG). Biopsies of patients with severe androgenetic or total baldness produced specimens showing nonspecific pathologic changes (39/50), while in 11 patients with a hair-bearing scalp histopathologic examination, changes were specific. The clinicopathologic similarities between EPDS and PPG suggest that EPDS should be included in the spectrum of autoinflammatory dermatoses. Clinicians could consider the possibility of associated disorders rather than managing EPDS as a sui generis skin disorder.