Light and ultrastructural study of reactive perforating collagenosis.

In 1967, Mehregan et al described a new and distinct clinicopathologic entity that they called reactive perforating collagenosis (RPC). This rare disease is classified with a group of disorders that involve the transepithelial elimination of histochemically altered dermal tissue. In RPC, minor trauma such as an insect bite, scratch, or pilosebaceous infection alters the collagen fibers in the papillary dermis. The histochemically altered but ultrastructurally intact collagen elicits both a dermal and epithelial response. For the case presented, it is our purpose to demonstrate transepithelial elimination of collagen fibers by ultrastructural study, thereby supporting the recognized histochemical observations.