Obstruction or renal allograft rejection--potential clinical markers of BK virus nephropathy

Abstract

Sir, BK virus (BKV)-associated nephropathy in renal transplant recipients is an emerging cause of allograft dysfunction and transplant loss.1,,2 BKV is a human polyomavirus which is a member of the Papovaviridae family. These are non-enveloped viruses of small virion size with a closed, circular double DNA-stranded genome.3 Polyomaviruses are ubiquitous in nature and were first isolated from the urine of a renal transplant patient who developed ureteral stenosis post-operatively.3 Up to 80% of adults are seropositive for BKV with the virus subsequently remaining dormant in the uroepithelium. The majority of primary infections are asymptomatic or minimally symptomatic. The incidence of BKV nephropathy among renal transplant recipients is as high as 5%.1 The majority of infections occur within the first 3 months after transplant; however, infections occurring >2 years after transplantation have been reported.4 BKV disease is associated with haemorrhagic and non-haemorrhagic cystitis, ureteric stenosis and tubulointerstitial nephritis.4 Between 30% and 50% of patients with BKV nephropathy develop progressive renal dysfunction leading to eventual allograft loss.5 The risk factors for BKV are not known but it is suggested to be a disease associated with modern day immunosuppression. Apart from the histopathological likeness to acute rejection and hence misdiagnosis, BKV infection can also manifest as ureteric stenosis during the early post-transplant period.1 Reduction in immunosuppression has yielded varying results and evidence with cidofovir and ciprofloxacin are promising.4–8 We report two cases of BKV in renal transplant patients to highlight important teaching points in BKV nephropathy. The first patient was treated for ureteric stenosis and was later diagnosed to have BKV nephropathy resulting in graft loss despite the use of cidofovir and the other developed chronic allograft nephropathy (CAN), which stabilized with immunosuppression reduction. ### Case 1 A 53-year-old female with end stage kidney disease …