BK Virus

 

Clinical Background

BK virus is a polyoma virus in the same family of viruses as human papilloma and JC virus and has become recognized as an important causal infectious agent in complications after kidney transplant.

Epidemiology

  • Prevalence
    • Primary BK infection generally occurs in childhood (without specific symptoms)
      • 90% are seropositive by 10 years
    • 1-5% of kidney transplant patients are affected
  • Transmission
    • The virus is presumably transmitted via respiratory droplets
    • Other speculated modes include urine, semen, blood transfusion and organ transplantation

Organism

  • Double-stranded DNA virus
  • Human papillomavirus (genetically similar to JC virus)
  • After primary infection, BK virus becomes latent in the kidneys and urinary tract
  • Reactivated BK virus infection occurs with immunosuppression

Clinical Presentation

  • Clinical disease is rare in immunocompetent adults
  • BK virus infections are a cause of morbidity and mortality for patients with hematologic malignancies and transplants (most often bone and kidney)
  • Illnesses caused by BK virus
    • Nephropathy and graft loss in renal transplant patients
      • BK virus allograft nephropathy (BKVAN) present in up to 8% of kidney transplant patients
        • Tubulointerstitial nephritis
          • Most common manifestation
          • Leads to irreversible graft failure in 40-50% of patients
        • New immunosuppressive regimens may increase the risk of BKVAN
    • Hemorrhagic cystitis and renal impairment in patients with hematologic malignancy and bone marrow transplant

Treatment

  • Bone marrow/hematologic malignancies
    • Supportive in hemorrhagic cystitis; most patients recover
    • Refractory cystitis may be catastrophic
      • Poor response to antiviral therapy
  • Renal transplant patients
    • If no active rejection present, judicious reduction of immune suppression is acceptable and usually decreases viral load