Polyomavirus nephropathy in renal allograft

Background: While polyomavirus nephropathy (PVN) is recognized as an emerging cause of graft loss in renal transplants, the prevalence rate of PVN in renal grafts is unclear in Taiwan. Methods: Biopsies (n = 412) from 323 Taiwanese renal transplant patients were retrospectively analysed. PVN was diagnosed by the characteristic viropathic change in epithelial cells under light microscopic examination and a positive immunohistochemistry staining of anti-SV40 large T antigen. The viral cytopathic changes, interstitial inflammation, fibrosis and tubular atrophy were semiquantitatively assessed, based on the Banff 1997 classification and scoring for renal allograft. Results: Seventeen cases were identified with evidence of PVN; the prevalence rate is 5.26%. Compared with non-PVN patients, they were more likely to have had previous rejection episodes, higher graft loss and shorter graft survival. Conclusion: This retrospective study showed that we have similar findings to other reports with at least 5% prevalence of PVN and that patients diagnosed early do better, while those diagnosed with severe inflammation or damage do worse or are likely to lose their grafts.