Perforating lichen nitidus in the setting of atopic dermatitis.

Perforating lichen nitidus is a rare subtype of lichen nitidus, with approximately 11 cases reported worldwide. Lesions typically present in young male patients at sites prone to mechanical irritation, including the hands, feet, forearms, elbows, and knees. Classic histopathologic features of perforating lichen nitidus show a lymphohistiocytic infiltrate within the papillary dermis between hyperplastic rete ridges with transepidermal elimination of dermal contents. Very few cases are reported in the literature of lichen nitidus and its association with atopic dermatitis. This is the first case describing perforating lichen nitidus in a patient with a history of atopic dermatitis being treated with dupilumab injections. Lesions of perforating lichen nitidus worsened with successful treatment of atopic dermatitis. These findings suggest a unique pathophysiology of perforating lichen nitidus lesions.