Features of Lichen Planus and Psoriasis on Ex Vivo Confocal Imaging and Histopathologic Correlation

Abstract

Lichen Planus is an idiopathic inflammatory skin and mucous disease, typically characterized by pruritic, violaceous papules that favour the extremities and histologically featured by a dense, band-like lymphocytic infiltrate and keratinocyte apoptosis with destruction of the epidermal basal cell layer. Ex vivo confocal imaging shows dense band of bright small and round nuclei distributed in the dermis immediately below the epidermis. Psoriasis is an immune-mediated polygenic skin disorder in which the most common clinical setting includes sharply demarcated, scaly, erythematous plaques involving scalp, elbows, and knees. The histological findings include acanthosis with elongated rete ridges, hypogranulosis, hyper- and para-keratosis, dilated blood vessels and perivascular infiltrate of lymphocytes with neutrophils singly or within aggregates in the epidermis. Ex vivo fluorescent confocal imaging shows small, flat, bright nuclei distributed throughout the parakeratosic epidermis and subcorneal or intracorneal Munro microabscesses composed by irregular polylobate bright nuclei representing the neutrophils. In both Lichen Planus and Psoriasis on digital H&E mode all bright fluorescent structures appear dark and purple-blue, with a correspondence to hematoxylin stained hyperchromatic nuclei.