title: Prevalence, characteristics, and outcome of BK virus nephropathy in Japanese renal transplant patients: analysis in protocol and episode biopsies.
abstract: BACKGROUND
  BK virus nephropathy (BKN) is recognized as a cause of graft loss in renal transplant patients. This may be related to the introduction of new and potent immunosuppressive regimens. In Japan, our experience regarding its prevalence, clinical significance, and outcome is still limited. In this study, our primary purpose is to outline the prevalence, outcome, and clinical characteristics of BKN as observed at Osaka University Hospital.
  
  
  METHODS
  We retrospectively analyzed 112 biopsy specimens from 87 renal transplant patients. All transplantations were from living donors. Of the 112 biopsy specimens, 71 were from protocol biopsies and 41 were from episode biopsies. Calcineurin inhibitors and corticosteroid were used in all patients (tacrolimus 32 and cyclosporin 55). In addition, azathioprine was used in 43 patients, mizoribine was used in 24 patients, and mycophenolate mofetil was used in 20 patients. BKN was diagnosed by light microscopic examination and a positive immunohistochemical staining of anti-SV40 antibody in a biopsy specimen. In order to investigate the outcome and potential risk factors of patients with different histological staging, we divided the patients into groups A (mild histological change) and B (moderate or severe histological change).
  
  
  RESULTS
  Of the 87 patients, six were diagnosed with BKN. There were no significant differences between BKN patients and non-BKN patients, except for the number of patients with graft loss (p < 0.001). Of the six BKN patients, three were in group A, and three were in group B. We recognized a significant difference between group A and group B in terms of anti-rejection treatment including glucocorticoid, tacrolimus trough levels of over 8 ng/mL, episode of acute rejection within 1-month post-transplantation, and the time period between transplantation and BKN diagnosis.
  
  
  CONCLUSIONS
  This is the first report of BKN in Japanese renal allograft recipients. In our hospital, the prevalence, risk factors, and outcome were similar to those previously for non-Japanese recipients.
authors.affiliation: Department of Urology Graduate School of Medicine, Osaka University, Osaka, Japan.
authors.forename: Yukiomi
authors.initials: Y
authors.lastname: Namba
authors.forename: Toshiki
authors.initials: T
authors.lastname: Moriyama
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kyo
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Imamura
authors.forename: Yi
authors.initials: Y
authors.lastname: Shi
authors.forename: Naotsugu
authors.initials: N
authors.lastname: Ichimaru
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Oka
authors.forename: Shiro
authors.initials: S
authors.lastname: Takahara
authors.forename: Akihiko
authors.initials: A
authors.lastname: Okuyama
mesh_terms: D000328:Adult; D001739:BK Virus; D001706:Biopsy; D002985:Clinical Protocols; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects* / Q000276:immunology; D007564:Japan / Q000453:epidemiology; D007668:Kidney / Q000473:pathology; D016030:Kidney Transplantation / Q000009:adverse effects* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009393:Nephritis / Q000453:epidemiology* / Q000473:pathology / Q000601:surgery / Q000821:virology; D027601:Polyomavirus Infections / Q000150:complications*; D015995:Prevalence; D012189:Retrospective Studies; D016896:Treatment Outcome; D014412:Tumor Virus Infections / Q000150:complications*
chemical_list: D007166:Immunosuppressive Agents