Pityriasis rosea in a patient with epidermolysis bullosa dystrophica.

A patient with clinical and histologic features of epidermolysis bullosa dystrophica-recessive (EBD-R) developed superimposed clinical lesions of pityriasis rosea (PR). Electron microscopy showed distinct "blebbing" of basal cells at the basement membrane zone in clinically normal skin of a non-predilected area, as well as in scarred skin from a predilected area and a lesion of PR. An increased susceptibility of the basement membrane zone to proteolytic enzymes is suggested as a possible hypothesis to explain these observations.