[Nevoid acquired perforating dermatosis of vellus hair follicles--a new entity? Case report with immunohistochemical studies].

We report on a 45-year-old male patient with a 15-years history of partly excoriated and inflamed lesions of verruccous-papular character, arranged in a linear naevoid fashion on the extensor side of the right arm and shoulder. The lesions were not related to a dermatoma but seemed to be located in the Blaschko's lines. On histology an epidermal invagination was found, conspicuously arranged over proliferating vellus hair follicles, which were increased in number as in a hamartoma. The rete ridges were directed towards early anagens of the vellus hairs with consecutive crateriform invagination of the epidermis with parakeratosis and basophilic debris on the innermost layer of the invagination. Serial sections allowed demonstration of incomplete and complete perforation with accumulation of neutrophils. Immunohistochemistry revealed marked staining of basal cells of the proliferating epidermal keratinocytes with cytokeratins 14 and 18 within the lesion. No association with diabetes or renal insufficiency and no familial background could be found.