Peripheral Blood Next-Generation RNA Sequencing as an Adjunctive Tool in the Evaluation of Borderline T-Cell-Mediated Rejection in BK Virus Nephropathy.

Distinguishing BK virus nephropathy from T -cell -mediated rejection remains a clinicopathological challenge in kidney transplants, because the 2 entities may share overlapping histological features while requiring opposite therapeutic approaches. We report a kidney transplant recipient with biopsy -proven BK virus nephropathy who later underwent repeat biopsy showing low -level BK virus nephropathy with borderline T -cell -mediated rejection. Despite histological concern for rejection, the broader clinical picture did not support clinically significant T -cell -mediated rejection; specifically, serum creatinine remained stable, BK viral load showed marked improvement, donor -specific antibodies were negative, and there were no vascular or microvascular features of active rejection. A peripheral blood next-generation RNA sequencing gene expression profile yielded a low -risk acute rejection score of 6. Antirejection therapy was deferred, immunosuppression was not escalated, and the patient remained clinically stable. This case highlights the potential adjunctive role of peripheral blood RNA profiling for resolution of histologically ambiguous cases of BK virus nephropathy and borderline T -cell-mediated rejection.