Clinical and Histologic Features of Nevus Comedonicus
Three unrelated subjects presented with linear patches of comedones on distinct body sites. NC101, a 43-year-old woman, had a lesion on the back that featured numerous dilated follicular ostia and comedones, with a scar inferiorly at the site of a prior inflammatory lesion (A). NC102, a 10-year-old boy, had a lesion on the thigh that featured numerous comedones and atrophic scars at the sites of prior inflammatory lesions (B). NC103, a 19-year-old woman, had a hairless patch on the scalp. The patch subsequently never grew hair and developed multiple comedones and inflammatory cysts (C). Intervening skin appeared grossly normal in all subjects. Histopathologic examination of affected scalp excision tissue in subject NC103 revealed normal hair follicles (white arrows) adjacent to affected follicles (black arrow), which show dilated follicular ostia, marked acanthosis and papllimatosis of the outer root sheath, and large cystic structures filled with keratin in the deep dermis (D). Examination of tissue excised from the back of subject NC101 shows an isolated follicle with a dilated ostium, acanthosis and papillomatosis of the outer root sheath, and accumulated keratin in place of a hair shaft (E). In both cases, interfollicular epidermis appears to be normal. Scale bars represent 1 mm.