Renal Failure Five Years After Lung Transplantation Due to Polyomavirus BK‐Associated Nephropathy

Polyomavirus‐associated nephropathy (PyVAN) is rare in nonrenal solid organ transplantation and only limited information is available from single cases. We describe a 67‐year‐old female presenting with hypertension and progressive kidney failure due to PyVAN 60 months after lung transplantation. Plasma BK virus (BKV) loads were 4.85 log₁₀ copies/mL at diagnosis and cleared slowly over 14 months after switching from tacrolimus, mycophenolate and prednisone to low‐dose tacrolimus, sirolimus and leflunomide, the latter being discontinued for anemia and diarrhea. BKV‐ and JC virus‐specific immunoglobulins were detectable prior to transplantation. Only BKV‐specific IgG and IgM increased during follow‐up. BKV‐specific T cells were detectable in blood following in vitro expansion, but cleared with reincreased sirolimus, yet BKV viremia remained undetectable. We identified eight other cases of PyVAN in nonrenal solid organ transplantation including lung (n = 1), heart (n = 6) and pancreas (n = 1). Overall, diagnosis was later than commonly seen in kidney transplants (median 18 months, interquartile range 10–29). Seven patients were male, five received triple immunosuppression consisting of tacrolimus, mycophenolate, prednisone. Immunosuppression was reduced in four cases and cidofovir and/or leflunomide administered in five and two cases, respectively. Renal function deteriorated in five requiring hemodialysis in four. We discuss mTOR inhibitors versus cidofovir and leflunomide as potential PyVAN rescue therapy.