Human BK Polyomavirus Nephropathy (BKVN) In Non- Kidney-Transplant Patients

Abstract

Abstract Introduction/Objective Human BK polyomavirus nephropathy (BKVN) occurs in up to 10% of renal transplant recipients, and can result in graft loss. Transplant biopsy is the gold standard to diagnose BKVN, and SV40 immunohistochemical (IHC) staining is helpful in confirming the diagnosis. BKVN is uncommon outside the setting of renal transplantation. To understand more about its occurrence in other contexts, we reviewed our renal biopsies files for cases of BKVN. Methods Our renal biopsy files for the past 20 years were reviewed for all cases with a diagnosis of BKVN or polyoma virus infection, and the clinical characteristics of the affected patients noted. Results Evidence of BKVN was found in 44 renal biopsies, of which 39 (86%) were renal transplant patients. Of the remaining five patients (14%), two had undergone heart transplantation, one lung transplantation, one was undergoing chemotherapy for acute lymphoblastic leukemia, and one patient had active HIV infection. All patients had elevated serum creatinine, and four out of five patients had documented BK viremia. Four of the five biopsies showed typical tubular injury with viral nuclear cytopathic changes (inclusions). In the lung transplant patient, the biopsy showed advanced chronic tubulointerstitial injury without distinct viral inclusions, but SV40 staining confirmed the presence of BK virus antigen. Conclusion The BKVN is distinctly uncommon outside the context of kidney transplantation. In our series, 14% of patients with BKVN were not kidney transplant recipients, but all were immune compromised in some fashion. The pathologic features of BKVN appear similar, regardless of whether the host is a renal transplant recipient or not. Although uncommon, it is important to consider the possibility of BKVN in non-renal transplant patients with persistent or progressive renal dysfunction.