Vesiculopustular Pyoderma Gangrenosum 2

Vesiculopustular pyoderma gangrenosum is an uncommon variant of pyoderma gangrenosum characterized by pustular, vesiculopustular, or ulcerative lesions arising in the setting of a sterile, pathergic neutrophilic dermatosis. It may occur in children and can be associated with inflammatory bowel disease; oral involvement may show overlapping features with pyostomatitis vegetans. Histologically, the process may show intense neutrophilic inflammation with folliculocentric tissue destruction, neutrophilic dermolysis, epidermal undermining, necrosis, and secondary vasculitic changes. Because of the overlap with necrotizing Sweet syndrome and infectious pustular processes, clinicopathologic correlation and negative infectious studies are important.

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Slide 1: Figure 1. 3-year-old previously healthy boy with several weeks of fever and pustular/ulcerative lesions involving the skin and mouth. H&E shows an extensive pathergic, neutrophil-rich process centered on and destroying a hair follicle (40×).

Slide 2: Figure 2. H&E shows folliculocentric neutrophilic dermolysis with striking undermining of the interfollicular epidermis and frank epidermal necrosis (100×).

Slide 3: Figure 3. H&E shows angiocentric neutrophilic and mononuclear inflammation with mural and luminal fibrin deposition. These vasculitic changes are largely confined to zones of neutrophilic dermolysis and are interpreted as secondary vascular injury rather than the primary driver of the process (200×).

Slide 4: Figure 4. Away from the zone of necrotizing neutrophilic dermolysis, H&E shows a lymphomononuclear infiltrate with a minor neutrophilic component, accentuated around nerves and blood vessels and extending into the adventitial dermis and fat (200×).

Slide 5: Figure 5. CD3, CD4, and CD8 immunohistochemistry highlight the T-cell component of the infiltrate, with predominance of CD4-positive cells over CD8-positive cells (40×).

Slide 6: Figure 6. CD14 and CD11c immunohistochemistry highlight monocytes and monocyte-derived dendritic cells, respectively, supporting a mixed monocyte/T-cell infiltrate likely contributing to secondary neutrophil recruitment (40×).