Apoptosis expression in various cutaneous diseases

Background: Cell death is divided into two types, cell necrosis and apoptosis. In contrast to cell necrosis, an apoptotic cell is ingested by phagocytes and apoptosis is not accompanied by local inflammatory cells. Recently, apoptosis is considered to be involved in the pathogenesis of autoimmune diseases. Objective: We investigated the presence of apoptotic cells in discoid lupus erythematosus, lichen planus, and psoriasis which are cutaneous autoimmune diseases, and also in erythema multiforme, which is not an autoimmune disease and of which characteristic in histopathologic features is necrotic keratinocytes. Methods: A total of forty-six skin biopsy specimens were chosen. The specimen is made up of ten of each discoid lupus erythematosus, lichen planus, psoriasis, erythema multiforme and six of normal skin. We performed TUNEL stain on each specimen to observe apoptotic cells in the epidermis and dermis. The mean numbers of apoptotic cells were compared using the Kruskal-Wallis test and post hoc according to Conover. Results: In discoid lupus erythematosus, apoptotic cells were observed as the most common disease in the epidermis and also in the dermis. In lichen planus, apoptosis was rarely observed in the epidermis, but was observed as the second common disease in the dermis. In psoriasis, apoptosis was rarely observed in both the epidermis and dermis. In erythema multiforme, apoptosis was observed in both the epidermis and dermis, and especially observed as the second common disease in the epidermis among four diseases. Conclusion: Apoptosis may contribute to pathogenesis of discoid lupus erythematosus and also in part to lichen planus and erythema multiforme. However, in psoriasis, apoptosis was rarely observed and resistance to apoptosis may be involved in the pathogenesis of psoriasis.