The “Borderline” Renal Allograft Biopsy: Differential Diagnosis, Pitfalls, and Challenges

Abstract

A diagnostic category termed “borderline changes suspicious for acute rejection” is included in the Banff schema for allograft pathology to recognize biopsies that do not fulfill the histological criteria for T-cell–mediated rejection. Although some cases represent early stage or treated immune injury, others represent intercurrent clinical conditions such as acute tubular injury, calcineurin inhibitor toxicity, infection, and obstructive uropathy. We document the spectrum of graft dysfunction associated with this diagnosis by reporting a patient who initially fell in the borderline category. Further investigation demonstrated acute antibody-mediated injury, which was treated appropriately but complicated by polyomavirus BK viremia. This triggered reduction in the dose of immunosuppression, which led to rebound grade 1B T-cell–mediated rejection superimposed on antibody-mediated rejection. Inability to maintain the right balance of immunosuppression that could effectively control both rejection and infection led to graft loss. This case illustrates how management of the patient with borderline changes at biopsy requires detailed clinicopathological correlation and careful monitoring.