Clinicopathologic features of polyomavirus nephropathy: Our experience - A retrospective observational study

Abstract

Introduction: Polyomavirus nephropathy (PVN) is now being frequently encountered in renal transplant recipients receiving highly potent immunosuppressive drugs and has emerged as an important cause of allograft loss. In this study, we tried to study the clinical and morphological features while incorporating the latest Banff 2018 classification of PVN and correlating it with graft outcomes. Materials and Methods: This was a retrospective study including ten patients with biopsy-proven PVN. The risk factors, clinical, histomorphological, and immunohistochemical features of all the patients were studied. We scored the intrarenal polyomavirus load and Banff interstitial fibrosis as described by Banff 2018 working group. Results: There were 6 male and 4 female patients and the mean age at the time of biopsy was 42.5 ± 10.8 years. All patients were on triple immunosuppression and the mean transplant duration to the time of diagnosis was 6.98 ± 4 months. The mean serum creatinine at the time of biopsy was 2.73 ± 1.12 mg/dl. A prior history of antibody-mediated rejection was present in two patients. All ten biopsies showed tubular epithelial basophilic, intranuclear inclusions suggestive of BK virus which was confirmed by positivity for SV40 antigen on immunohistochemistry (IHC). As per the Banff 2018 classification, seven biopsies were categorized as Class 2 and three were class 3. On follow-up, three patients went into graft loss, five patients had persistent graft dysfunction, and two expired. Conclusion: PVN is an important cause of renal dysfunction and premature allograft loss. Light microscopy for viral cytopathic changes aided by IHC with SV40 is essential for the diagnosis of PVN. The Banff scheme of classification is helpful in predicting the prognosis. It is important to diagnose PVN and differentiate it from rejection for appropriate management.