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.

Infundibular hyperkeratosis, hyperplasia of the follicular epithelium and perifolliculitis are major histopathological characteristics of hidradenitis suppurativa/acne inversa. These apparently precede rupture of the follicle. In particular, hyperplasia of the follicular epithelium probably marks the beginning of sinus formation, which usually spreads horizontally. Psoriasiform hyperplasia of the interfollicular epidermis with subepidermal inflammatory infiltrate might be interpreted as an inflammation-driven process basically identical to that which is evident at the terminal follicle. However, it does not lead to harmful and progressive sequelae like those (rupture, sinus tracts) seen at the terminal follicles.

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.

Five patients with generalized slate-gray discoloration of the skin have been diagnosed histologically as argyria in the last 35 years in the Department of Dermatology and Venereology of Rostock and Halle. Light microscopically, there was visible black pigmentation in histiocytes, fibroblasts, and multinucleated giant cells of the dermis. In the transmission electron microscope (TEM), the authors observed electron-dense deposits inside lysosomes and residual bodies of phagocytes as well as outside the cells in the connective matrix. These deposits were identified by elemental analysis in TEM and electron energy loss spectroscopy (EELS) as well as scanning electron microscope (SEM) and energy dispersive x-ray analysis (EDX) containing silver and sulfur. Therefore, they seem to consist of silver sulfide. Argyria is of low medical relevance and is very rarely induced because of silver-containing drugs. Nevertheless, there are still a lot of silver products on the market, easily available over-the-counter. Therefore, argyria should not be forgotten or missed in the diagnostics of human dermis.