Revisit of Polyomavirus Nephropathy Grading in Renal Allograft Recipients According to the Banff 2019 Working Group Classification: A Study From a Large Transplant Center in South India.

Background In renal transplant patients, the biopsy-proven incidence of polyomavirus nephropathy (PVN) is approximately 5%. There is no consensus in the morphologic classification of definitive PVN, which is attempted in the Banff 2019 Working Group classification, which groups histologic changes, reflects clinical presentation, and facilitates comparative outcome analyses. This study aims to analyze the clinical and histopathological findings and outcomes among the three classes in the recent classification. Materials and methods The study was conducted in the department of pathology and nephrology over a period of six years. All cases diagnosed as PVN on renal allograft biopsies were included. The clinical and biochemical findings were obtained from hospital records. Histopathology slides were reviewed and classified according to Banff 2019 criteria and were analyzed with clinical, laboratory, histopathological parameters along with the clinical outcome. Results Out of 205 renal transplants performed during the study period, 14 patients (6.8%) were diagnosed with PVN. The mean age of diagnosis was 38 years, with a Male: Female ratio of 1.8:1. The median period of diagnosis of the viral infection after transplant was 10 months. Histomorphology grading according to Banff 2019 revealed four cases (28.5%) in PVN class 1, eight cases (57.2%) in PVN class 2, and two cases (14.3%) in PVN class 3. Cases in PVN class 1 presented early. PVN class 1 was associated with a single type of inclusion, and multiple type inclusions were observed in higher classes. Associated diseases were thrombotic microangiopathy (TMA), borderline cellular rejection, antibody-mediated rejection (ABMR), and concomitant infections. PVN class 1 had a better outcome compared to PVN class 2 and class 3. Conclusion PVN1 was observed to have better clinical presentation and outcomes than PVN2 and 3; however, this could not be statistically concluded due to the low sample size and other associated diseases.