[Rosacea: histopathologic study of 75 cases].

Few histological studies have been devoted to rosacea, a common but ill-defined disease. We have examined histological sections obtained from 75 patients (41 men aged from 23 to 72 years and 34 women aged from 32 to 68 years), thereby confirming the diagnosis of rosacea. On average, 4 sections from each patient were examined. Blocks from cases with granuloma were serially sectioned in search of remains of hair follicles, degenerated collagen fibres and Demodex folliculorum. Elastotic degeneration, vasodilatation and the number of hair follicles were evaluated; the nature and disposition of inflammatory infiltrates were determined, and the presence of D. folliculorum was looked for. Elastotic degeneration, varying degrees of vasodilatation and inflammatory infiltrates were found in all patients. The infiltrates were predominantly lympho-histiocytic in 62 cases, neutrophilic around skin appendages in 6 cases, tuberculoid unrelated to appendages in 4 cases and tuberculoid surrounding follicle-related necrosis in 3 cases. The number and appearance of hair follicles seemed to be those normally observed in the regions where our specimens were taken. On the basis of histological, immunological and therapeutic arguments, it has been postulated that D. folliculorum was involved in the pathogenesis of rosacea, notably in its granulomatous form. In particular, several cases of granuloma containing the acarid in its core have been reported. However, the significance of such findings remains uncertain. D. folliculorum might induce the formation of a granuloma, but it is also possible that granulomas are consecutive to the destruction and resorption of hair follicles, the mite being "digested" more slowly than the epithelial structures.(ABSTRACT TRUNCATED AT 250 WORDS)