Lichen planus of the nail matrix with predominant plasma cell infiltrate.

Lichen planus (LP) is an inflammatory dermatitis of idiopathic origin that can involve the skin, mucous membranes, hair and nails. Histologically, LP is characterized by compact orthokeratosis, wedge-shaped hypergranulosis, irregular acanthosis, damage to the basal cell layer and a band-like inflammatory infiltrate in the upper dermis. Lymphocytes are the predominant cells making up the infiltrate, along with a few macrophages, eosinophils and plasma cells. In addition, melanophages are often found in the upper dermis adjacent to the damaged basal cells.(1) We describe a patient with a lesion of the toenail clinically and histopathologically consistent with LP, but with a band-like inflammatory infiltrate composed primarily of plasma cells. Previously, only three other cases of LP with plasma cell predominant infiltrate have been reported, none of which involved the nail matrix.