Background. Histologic findings of diabetic nephropathy (DN) are observed in allografts of patients with pretransplant (PreTx) diabetes mellitus (DM) and in patients who develop DM posttransplant (PostTx). Patients with allograft biopsies (Bx) were retrospectively studied to determine the incidence of recurrent and de novo DN and to ascertain what, if any, risk factors predispose to histologic DN in either patient population. Methods. From the renal transplant services at four hospitals from 1992 to 2000, the authors identified all patients with PreTxDM and PostTxDM (n=81). Those with renal biopsies performed ≥18 months PostTx were classified according to the presence or absence of histologic DN (Bx-positive, n=23; Bx-negative, n=35). Patients were then subdivided into four categories - recurrent DN (n=16), de novo DN (n=7), no recurrent DN (n=27), and no de novo DN (n=8) - for analyses. Results. Among these 58 patients, 74.1% had PreTx and 25.9% had PostTx diabetes. Of those with histologic DN, 69.6% were recurrent DN and 30.4% were de novo DN, making de novo DN at least as likely to develop as recurrent DN. After the onset of diabetes in the de novo population, the time to development of histologic DN was similar in the recurrent and the de novo patients (6.68±3.86 years vs. 5.90±3.13 years, P=0.66) and more rapid than previously reported. Apart from a more frequent family history of hypertension in patients with allograft DN compared with those without allograft DN, known risk factors for the development of native DN did not significantly differ among patients in the four cohorts. Proposed risk factors related to transplantation did not correlate with the development of recurrent or de novo DN. Conclusion. Among patients with histologic DN, de novo DN occurred at least as frequently as recurrent DN, and the time to onset of histologically apparent DN was more rapid than previously reported. Neither the usual clinical predictors of DN nor clinical variables related to transplantation clearly distinguished the group with DN from the group without it, potentially implicating novel mechanisms in its pathogenesis.
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