Nephrogenic fibrosing dermopathy.

This report details the histopathologic findings in a unique fibrosing disorder that recently emerged among patients with renal disease. The affected patients were initially identified among recipients of renal transplants at a single institution, but later cases at other centers were identified, and included patients receiving renal dialysis for a variety of different kidney diseases. The cutaneous changes consisted largely of indurated plaques and papules on the extremities and trunk. Systemic findings seen in scleromyxedema, which the condition resembles in some respects, were absent. By routine microscopy, the findings range from a very subtle proliferation of dermal fibroblasts in early lesions, to a florid proliferation of fibroblasts and dendritic cells in fully developed cases. Thick collagen bundles with surrounding clefts are a prominent finding, and a variable increase in dermal mucin and elastic fibers was usually evident with special stains. CD-34 positive dermal dendrocytes were floridly abundant, with dendritic processes aligned with elastic fibers and around collagen bundles in a dense network. Factor XIIIa and CD-68 positive mono-and multinucleated cells are also present in increased numbers. Electron microscopy highlighted increased elastic fibers closely apposed to dendritic cell processes. The entire dermis was commonly involved, with increased spindle cells, collagen, mucin, and elastic fibers extending through the subcutis along the septa of fatty lobules. In some instances, the process resembled a sarcoma on histopathologic examination. The recent emergence of this condition and the apparent clustering of cases in specific dialysis centers initially suggested a possible infectious and/or toxic agent. To date, however, no such agent has been identified. We propose the term "nephrogenic fibrosing dermopathy (NFD)" until a specific cause can be identified.