Study 2: BK polyomavirus nephritis and acute rejection tend to affect distinct groups of renal allograft recipients: a role for gender, race, and tacrolimus levels

Abstract

B K polyomavirus nephritis (BKN) has been linked to the newer immunosuppressants tacrolimus (TAC) and mycophenolate mofetil (MMF) even though risk factors for the disease have not been well defined. A recent study, however, suggested that BKN occurs as a complication of the treatment of acute rejection with methylprednisolone. To further examine the relationship between the treatment of acute rejection and BKN, we analyzed all kidney transplants performed at our center between January 1999 and August 2001 (n 286). After a mean follow-up of 622 63 days, we identified 9 cases of BKN (3.1%) using urine electron microscopy. Of these, 8 patients also underwent allograft biopsy, which confirmed the diagnosis. The mean time to diagnosis of BKN was 326 56 days. No patient with BKN had a history of acute rejection. During the same period, 59 (21%) patients were diagnosed with acute rejection and treated with methylprednisolone. The mean time to diagnosis of acute rejection was 197 40 days (P .01, vs time to diagnosis of BKN). None of these patients had subsequent development of BKN during the follow-up period. We compared the characteristics of patients with development of BKN with those of patients who had acute rejection and found that patients with BKN were more likely to be male (89% vs 53%, P .04) and white (78% vs 44%, P .05). Moreover, the mean TAC levels from the time of transplant to the time of diagnosis were higher in the BKN group than in the acute rejection group (12 1 vs 7 1 ng/mL, P .001). The treatment of BKN consisted mainly of a reduction in immunosuppression. MMF was discontinued in 7 of 9 patients, all of whom experienced disappearance of viruria (median time to negative result of urine electron microscopy, 147 days; range, 29-257) and remained independent of dialysis at last follow-up. In 2 of 9 BKN patients, MMF doses were only reduced. Neither patient had clearance of the viruria, and 1 ultimately lost the graft because of the viral infection. Conclusion: Our study does not show an association between acute rejection or its treatment and the development of BKN. Our findings suggest that these conditions tend to affect distinct groups of renal allograft recipients. Although there may be a potential relationship between high TAC levels and BKN, discontinuation of MMF was associated with clearance of viruria and preservation of renal function. From the Departments of Medicine, Nephrology, and Pathology, Duke University Medical Center, Durham, NC. © 2003 Elsevier Inc. All rights reserved. 0955-470X/03/1704-0000$30.00/0 doi:10.1016/j.trre.2003.10.019