Hidradenitis suppurativa (acne inversa) is a chronic suppurative and scarring inflammatory disease with predilection in the apocrine gland-bearing areas. Histological investigations in the 1990s showed keratotic occlusion of the terminal follicle structure to be the initial cause. Our investigations describe and reproduce the morphology and try to figure out very early lesions of HS. A total of 262 operative specimens from 60 patients were investigated by routine histology and 11 operative specimens by immunohistochemistry: HS is dominated by a heterogeneous histological image. 82% of the surgical specimens showed mild or pronounced follicular hyperkeratosis, whereas an isotopic hyperplasia of follicular epithelium was evident in 77%. Pronounced perifolliculitis was seen in 68% and rupture of the follicle structure in 28%. Features which had not so far been described in detail were: epidermal psoriasiform hyperplasia (43%) and subepidermal interfollicular inflammatory infiltrate (78%). In all 11 specimens, immunohistochemical investigations showed a perifollicular and subepidermal inflammation of CD-3-, CD-4-, CD-68-, CD-79- and CD-8-cells, the latter with a striking selective epitheliotropism. To conclude, we could show follicular hyperkeratosis and lymphocytic perifollicular inflammation as early patterns in pathogenesis, whereas rupture of the follicle structure takes place later. Finally, it seems that there are two hot spots of inflammatory events (perifollicular and subepidermal) composed of a comparable inflammatory cell mixture. The CD-8 cell epitheliotropism (follicular and epidermal) described here and its influence in follicular hyperkeratosis, in hyperplasia of follicular epithelium and in epidermal psoriasiform hyperplasia will be of further interest, for instance, concerning early pharmacological intervention.

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Background: The term ‘pilonidal sinus’ (PS) reflects an acute exacerbating, purulent, fistulating chronic inflammation located in the coccyx region. Systematic histological investigations are scarce, and the etiology has remained controversial. Methods: Histological and immunohistochemical characterization of totally excised material of 27 patients (68 specimens) with PS (no antecedent and no current clinical signs of hidradenitis suppurativa, HS) and its correlation with data on HS which we published earlier. Results: Follicular hyperplasia/hyperkeratosis and interfollicular epidermal hyperplasia are main features of PS. Early pathology seems to take place at terminal hair follicles, whereas sinus tract formations are a secondary event. Focused regions show an inflammatory mixed infiltrate consisting of CD3+, CD4+, CD8+, CD68+ and CD79+ cells. Conclusions: PS and HS have various common characteristics at the histological and immunohistochemical level. Considering PS as a unilocalized type of HS, risk factors known in the latter should henceforth be evaluated in PS as well.

Red ear syndrome (RES) is characterized by the attack-like occurrence of erythema, edema and dysesthesia of one or less frequently both ears. We report the case of a 31-year-old woman with stabbing pain and marked erythema and discrete edema of one ear, existing for 4 months, occasionally accompanied by burning and local hyperhidrosis. Differential diagnoses such as perichondritis, contact dermatitis, erysipelas and other infections were ruled out. Based on her history, the clinical pattern and the unremarkable further diagnostics, we diagnosed RES. A review of the literature is included.