Perforating porokeratosis of Mibelli

A case of perforating porokeratosis of Mibelli is presented. Clinically, the lesion was typical for porokeratosis of Mibelli. Nothing suggested a perforating disorder. Histologic examination revealed a well-developed cornoid lamella, and other histologic features typical of porokeratosis. A breach in the basal cell layer beneath the cornoid lamella resulted in transepithelial elimination of an amorphous material which on special stains proved to be collagen.