BK polyomavirus nephropathy after heart transplantation: A case report.

: We present a case of BK polyomavirus (BKV) nephropathy (BKVN) after heart transplantation (HTx). The patient was a male with non-ischemic cardiomyopathy who received HTx at the age of 56 years [serum creatinine (sCre) at the time of HTx: 0.89 mg/dl]. Following 3 months of standard triple immunosuppression using tacrolimus, mycophenolate, and corticosteroid, everolimus with reduced tacrolimus therapy was introduced because of cardiac allograft vasculopathy. However, renal function gradually deteriorated. BKVN was diagnosed via positive simian virus 40 antigen staining of renal biopsy specimens 46 months after HTx (sCre: 2.48 mg/dl). Decoy cells and elevated serum BKV load were also observed. After reduction of immunosuppression and monthly low-dose intravenous immunoglobulin administration, the serum BKV load decreased and sCre plateaued while on uneventful clinical course. Since renal function is an important prognostic factor after HTx, early diagnosis and intervention are crucial for successful BKVN treatment. Urine cytology should be performed during post-transplant screening for renal dysfunction. BK polyomavirus nephropathy (BKVN) is a critical issue following solid organ transplantation. However, reports regarding BKVN after heart transplantation (HTx) are sparse, possibly underestimating the significance of BKVN in HTx recipients, therefore case studies are crucial for the understanding of BKVN in HTx recipients. This case clearly demonstrated the clinical course of BKVN and highlights the important clinical implications for the diagnosis and management of BKVN in HTx recipients.