A Unique Case of Invagination of BK Polyomavirus-Infected Tubular Cells into Bowman’s Space in a Heart Transplant Patient With Acute Kidney Injury

A heart transplant recipient in his 60s with ischemic cardiomyopathy presented with worsening kidney function and BK virus viremia. He was previously treated with a high dose of steroids because of acute T-cell mediated rejection. On presentation, the individual was normotensive (121/82 mm Hg). Investigations showed a serum creatinine concentration of 4.6 mg/dL compared with a baseline of 1.5 mg/dL, hyaline casts in urine microscopy, a urine albumin-to-creatinine ratio of 40.7 mg/g, a serum BK virus polymerase chain reaction result of 9,900,000 copies/mL. Calculated panel reactive antibody results were 0% for human leukocyte antigen class I and class II. A kidney biopsy demonstrated invaginated tubular epithelial cells infected by BK virus into the Bowman’s space with classic nuclear inclusions, and the patient tested positive for SV40, which was also confirmed by electron microscopy (Fig 1). Classically described in kidney allografts, BK virus-associated nephropathy (BKVAN) is increasingly recognized in native kidneys of other nonkidney solid organ transplants; however, it is still rare. Only a few cases of BKVAN in heart transplant recipients have been reported.1Viswesh V. Yost S.E. Kaplan B. The prevalence and implications of BK virus replication in non-renal solid organ transplant recipients: a systematic review.Transplant Rev. 2015; 29: 175-180Crossref Google Scholar,2Shah A. Kumar V. Palmer M.B. et al.Native kidney BK virus nephropathy, a systematic review.Transpl Infect Dis. 2019; 21: 1-11Crossref Scopus (13) Google Scholar The prevalence of BKVAN in this population is not known, in part because it is not commonly tested for. Although viral cytopathic changes are mostly detected in tubular epithelial cells, glomerular involvement may occur in up to 24% of patients with BKVAN.3Chen X.T. Deng R.H. Yang S.C. et al.Pathological characteristics of BK polyomavirus-associated nephropathy with glomerular involvement.Ann Transl Med. 2020; 8: 923Crossref Google Scholar Intrarenal reflux in BKVAN has been reported.4Kawanishi K. Honda K. Koike J. et al.A preliminary study into the significance of intrarenal reflux in BK virus nephropathy after kidney transplantation.Transplant Direct. 2016; 2: 1-9Crossref Scopus (0) Google Scholar However, to our knowledge, no previous reports of invaginated tubular epithelial cells infected by BK virus into the glomerular Bowman’s capsule have been previously described. Mauro G. Montemayor-Villacobos, MD, Cindy Montero-Granados, MD, Salman Alfaifi, MD, Sonia Rodríguez-Ramírez, MD, MSc, and Carmen Avila-Casado, MD, PhD The authors declare that they have no relevant financial interests. Written informed consent was obtained from the patient for publication of this case report and any accompanying images. Received October 24, 2023. Accepted December 1, 2023, after editorial review by the Editor-in-Chief.

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