The pathogenesis of the transepithelial elimination of the collagen bundles in acquired reactive perforating collagenosis. A light and electron microscopical study.

Two cases of acquired reactive perforating collagenosis with poorly controlled diabetes mellitus were studied by histochemistry and by electron microscopy. In excoriated wound the necrotic mass on the bottom of the ulcer contained the collagen bundles which were continuous with the collagen bundles in the reticular layer. In the developing stage, the epidermis regenerated between the necrotic mass and the reticular dermis, and the collagen bundles in the reticular dermis were in continuity with those in the necrotic mass through the epithelial tunnels. The collagen in the epidermal channels did not degenerate ultrastructurally. In the mature lesion, collagen bundles being eliminated through the epidermis were surrounded by the fibroblasts at the basal cell layer. Collagen fibers were seen in the cytoplasm of these fibroblasts. From these findings, the mechanisms of the formation of the eruption in acquired reactive perforating collagenosis might be as follow: 1) In the developing stage, the regeneration of epidermis progresses between the necrotic mass and the reticular dermis, and among the collagen bundles. As a result, the collagen bundles remain in the channels of the epidermis. And then, 2) the regenerated epidermis makes the thick horny layer. As a result, the necrotic masses are lifted up and the collagen bundles are pulled up from the dermis through the epidermal channels.