Histopathologic comparison of nephrogenic fibrosing dermopathy and scleromyxedema

Background: Nephrogenic fibrosing dermopathy (NFD) clinically presents as indurated plaques and papules in patients with renal dysfunction. The differential diagnosis generally includes scleromyxedema (SMX), an idiopathic systemic disorder with cutaneous manifestations, in which patients also develop indurated papules and plaques. The two entities can be extremely difficult to distinguish microscopically. Histopathologic differences with immunophenotypic comparison, to our knowledge, have not been thoroughly studied. We compared these two entities with an emphasis on immunohistochemistry. Design: Nine biopsies diagnosed as NFD and seven biopsies diagnosed as SMX were retrospectively collected from the University of Pennsylvania Medical Center's surgical pathology and dermatopathology archives. Immunohistochemical staining for CD34, factor XIIIa, CD31, smooth muscle actin, CD68, and procollagen-I, as well as colloidal iron, were performed on each biopsy. Amount of expression for each of these markers, as well as degree of inflammation, for each biopsy was evaluated using a grading system of 0-3. Results: Overall, NFD and SMX showed similar expression for all markers except procollagen-I, which showed increased expression in SMX. Discussion: Although some immunophenotypic differences were found, our study did not demonstrate microscopic characteristics that can be easily used diagnostically to distinguish NFD from SMX. Clinical pathologic correlation is paramount in distinguishing these two entities.