Dynamic Leukocyte Populations Are Associated With Early- and Late-stage Lesions in Hidradenitis Suppurativa.

Hidradenitis suppurativa (HS) is a chronic inflammatory skin condition typically targeting the axillary and anogenital regions of the body. The massive inflammatory cell infiltrate produced in this cryptogenic condition has led investigators in the attempt to link particular inflammatory cell fractions and cytokines to disease development, and ultimately to disease treatment. This study qualitatively and quantitatively analyzes the white blood cell fractions of macrophages, B-lymphocytes, T-lymphocytes, plasma cells, and granulocytes in 104 HS lesions on formalin-fixed paraffin-embedded tissues using immunohistochemistry (IHC). Four dermis-associated epithelial categories were investigated from persons with HS: 15 unaffected HS skin (US), 19 distended but unruptured follicle epithelium (UF), 62 migrating stratified squamous epithelium (MSSE) from ruptured follicles, and 35 degraded migrating epithelial sheets (DMES). In addition, 27 control skin (CS) from persons without HS were evaluated. Analysis of cell counts indicated that non-migratory dermal epithelium (CS, US, and UF) stimulated very little inflammatory response. However, contrary to previous studies which indicated macrophages to be the chief inflammatory cell in HS, this study showed that plasma cells were the primary cell type present in early-stage HS lesions (MSSE), whereas granulocytes were the major cell population seen in late-stage HS lesions (DMES).