Native kidney BK virus nephropathy associated with chronic lymphocytic leukaemia.

BK virus nephropathy (BKVN) is a well-recognized complication of renal transplantation. Several cases of native kidney BKVN following other solid organ or bone marrow transplants have been reported. We describe a patient with chronic lymphocytic leukaemia who presented with deteriorating renal function with no history of solid organ or bone marrow transplantation. Renal biopsy demonstrated tubular injury characteristic of viral infection, confirmed as BK virus by immunohistochemistry and elevated serum BK viral titres. Treatment with leflunomide reduced serum viral titres and stabilized renal function. This is the first biopsy-proven case of native kidney BKVN in a patient with no previous transplantation history.