Lichenoid Tissue Reactions

Abstract

The lichenoid tissue reaction in which epidermal basal cell damage gives rise to a cascade of histologic events that produce lichenoid or poikilodermatous clinical pictures is outlined. Histologic features in the epidermis are degeneration of basal cells, preservation or increase of granular layer, orthokeratosis, and damage to melanocytes. In the dermis, lymphocytic infiltrate with tendency to invade the lower epidermal layers, capillary proliferation, and participation of histiocytes with formation of pigmented macrophages are characteristic. To the lichenoid and poikilodermatous groups of lesions is added a relatively new subgroup, exemplified by erythema dyschromicum perstans and lichen pigmentosus. The question is raised, whether the recent increase of pigmenting dermatitis of various type is due to the reaction of the skin of predisposed individuals to some as yet unknown environmental contaminant.