Late BK Nephropathy 15 years post kidney transplant following chemotherapy: A case report.

BK Polyomavirus (BKPyV) is an important risk factor for premature graft loss following kidney transplant. Current practice guidelines recommend screening for BK virus DNA for 2 years after kidney transplant as the risk of BK Polyomavirus associated nephropathy (BKPyVAN) wanes over time. This case report presents a unique scenario of late onset BKPyVAN 15 years following kidney transplant precipitated by administration of chemotherapy to treat multiple myeloma. A woman in her 60 s with no prior history of BKPyV was diagnosed with multiple myeloma 14 years after kidney transplant. Her immunosuppression was tapered to tacrolimus and prednisone before undergoing chemotherapy treatment for her multiple myeloma. Although the chemotherapy was effective in achieving remission of her myeloma, she developed worsening renal dysfunction without proteinuria. Kidney biopsy revealed positive SV40 staining and subsequent BK DNA serum PCR was found to be 236,000 copies/mL suggestive of BKPyVAN. Although incredibly rare, late onset BKPyVAN should be considered as a cause of sustained elevation in serum creatinine, new onset proteinuria, or new onset hematuria in kidney transplant recipients who have experienced an augmentation in immunosuppression such as patients undergoing chemotherapy for underlying malignancies.