BACKGROUND: Lichen nitidus and lichen striatus are often confused because they are thought to share similar clinical and histopathologic features. OBJECTIVE: The purpose of this study was to histopathologically and immunohistochemically evaluate the characteristic differences and common features between the two disorders. METHOD: Histopathological and immunohistochemical slides of 14 patients with lichen nitidus and 14 patients with lichen striatus were reviewed. Immunohistochemical staining with anti CD45RO, CD68, CD4, CD8 and CD20 antibodies was performed. RESULTS: 1) In lichen nitidus, the frequent histopathologic findings were liquefaction degeneration of the basal layer (100%), edema of the dermis within the areas of the infiltate (100%), and claw-like rete ridges (96.8%). 2) In lichen striatus, the frequent histopathologic findings were edema of the dermis within the areas of the infiltate (100%), liquefaction degeneration of the basal layer (92.9%), and perivascular inflammatory cell infiltrate (92.9%). 3) The majority of the cells in the infiltrate of lichen nitidus were T lymphocytes mixed with histiocytes. In most cases, CD4+ T lymphocytes predominated CD8+ T lymphocytes. 4) However, in lichen striatus, infiltrating cells in the dermis were composed dominantly of T lymphocytes, with a minority of histiocytes. CD8+ T lymphocytes were also found to outnumber CD4+ T lymphocytes. CONCLUSION: Our study did differentiate each disease as having distinctive characteristics and differences. Furthermore, the immunologic pathophysiology of lichen nitidus and lichen striatus was proved to be distinctive. Therefore, we conclude that these two diseases are not in the spectrum of the same disease, but separate disease entities which are indeed different from each other.
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