RESUMO
Lichen planus (LP) is a mucocutaneous inflammatory dermatitis of idiopathic origin that can involve the skin, mucous membranes, hair, and nails. LP has an associated set of characteristic histopathologic findings which include hyperkeratosis, vacuolization of the basal layer, Civatte bodies, wedge-shaped hypergranulosis, band-like lymphocytic infiltrate at the dermal epidermal junction, eosinophilic colloid bodies in the papillary dermis, and pigment incontinence. The infiltrate is usually composed of lymphocytes with few histiocytes, mast cells, and macrophages. The presence of plasma cell predominant infiltrate in LP has only been reported in four previous cases and 2 other cases of lichen nitidus. The authors report another 2 cases of LP with predominate plasma cell infiltrate in 2 female patients on the legs. The differential includes a drug-induced lichenoid reaction with predominate plasma cell infiltrate. However, there have been no case reports of that type of reaction. Because plasma cells are seen commonly in certain infectious diseases, malignancy, and macroglobulinemia, it is prudent to rule out those entities. Our patients responded well with a class 1 topical steroid, with improvement of their lower leg lesions within 1 month of treatment.