The Role of the Epidermis in the Histopathogenesis of Lichen Planus

Abstract

Detailed enzyme histochemical studies were performed on 18 biopsy specimens of lichen planus. The majority of the biopsies came from patients with acute lichen planus, but 3 were obtained from hypertrophic lesions of long standing. The most striking finding was a marked apparent depression of respiratory enzyme activity in the affected epidermis using techniques for the demonstration of succinic dehydrogenase, cytochrome oxidase and NAD diaphorase activity. Decreased epidermal cell turnover, damage to lower epidermal cells where these enzymes normally show maximal activity or local anoxia are amongst the factors which are considered to be responsible for this enzyme depression. No increase in various hydrolytic enzymes associated with lysosomal activity, such as nonspecific esterase and acid phosphatase, could be demonstrated in areas where basal cell necrosis was a marked feature. A great reduction in the number of melanocytes was indicated by the dopa-oxidase reation in active lesions. The relevance of these various findings with particular reference to the role of the lower epidermis in the histogenesis of lichen planus is discussed.