Erosive pustular dermatosis of the scalp: A neutrophilic folliculitis within the spectrum of neutrophilic dermatoses: A clinicopathologic study of 30 cases

Background: It is general opinion that histopathology is nonspecific and of little value in diagnosing erosive pustular dermatosis of the scalp (EPDS). Objectives: Clinicopathologic correlation of erosive pustular dermatosis of the scalp. Methods: We reviewed the clinical and pathologic records of patients with a clinicopathologic diagnosis of EPDS between 2011 and 2016 at the Dermatopathology Unit of Turin University. Results: Thirty elderly patients with EPDS were identified (22 men and 8 women). Androgenetic alopecia was present in 19 of 30 patients. Triggering factors included mechanical trauma in 10 of 30 cases, surgical procedures in 4 of 30 cases, and herpes zoster in 1 of 30 cases. Three patients were affected by autoimmune disorders. The vertex was the most common location. Disease presentation varied markedly from tiny, erosive, scaly lesions to crusted and hemorrhagic plaques, mimicking pustular pyoderma gangrenosum. The pathologic changes differed according to lesion type and disease duration. Interestingly, a spongiotic and suppurative infundibulo-folliculitis was observed in 8 of 30 cases. Limitations: This was a retrospective study. Conclusions: We believe that the primary lesion of erosive pustular dermatosis of the scalp is a spongiotic, pustular superficial folliculitis. The clinicopathologic similarities with other neutrophilic dermatoses, such as pustular pyoderma gangrenosum, suggest this condition should be included in this spectrum, where pathergy plays a pathogenetic role.