A case of Woringer and Kolopp disease, Pagetoid reticulosis, is described. Clinical features include a ring or a target pattern of erythematosquamous infiltrated skin lesion. The characteristic histological aspect of dense epidermal infiltrate by abnormal cells with a spread dermis was observed. Ultrastructural findings include cytoplasmic granules with a round electron dense core and close relationship to neurities, 2 features of the Merkel cell of human normal epidermis. By comparing this patient with the already reported cases of Woringer and Kolopp disease it seems likely that this is a unique disease with no relationship with cutaneous lymphoma but which is defined by a Merkel cell proliferation.