Wednesday 14 September 2005
Case 272 : BK Virus nephritis
Definition : The BK virus is a member of the polyomaviruses family. Past infection with the BK virus is widespread, but significant consequences of infection are uncommon, with the exception of the immunocompromised and the immunosuppressed.
BK polyoma virus has a worldwide distribution in the human population. Primary BK infection takes place during childhood, with the virus remaining latent in many sites. Immunosuppressive states can lead to viral reactivation associated with many clinical sequelae.
The BK virus was first isolated in 1971 from the urine of a renal transplant patient, initials B.K.
The BK virus is similar to another virus called the JCV since their genome sequences share 75% homology. Both of these viruses can be identified and differentiated from each other by carrying out serological tests using specific antibodies or by using a PCR based genotyping approach.
BK virus infection can be associated with renal interstitial inflammation, tubulitis without viral cytopathic effect, and negative in situ hybridization for viral DNA.
BK virus nephritis - BK virus nephropathy
- BK virus tubulitis
BK virus pneumonia (BK polyoma viral pneumonia) (16153469)
- intranuclear large basophilic viral inclusions with ground-glass appearance mainly in type II pneumocytes (16153469)
BK virus encephalitis
The BK virus rarely causes disease since many people who are infected with this virus are asymptomatic. If symptoms do appear, they tend to be mild: respiratory infection or fever. These are known as primary BK infections.
The virus then disseminates to the kidneys and urinary tract where it persists for the life of the individual. It is thought that up to 80% of the population contains a latent form of this virus, which remains latent until the body undergoes some form of immunosuppression.
Presentation in these immunocompromized individuals is much more severe. Clinical manifestations include renal dysfunction (seen by a progressive rise in serum creatinine), and an abnormal urinalysis revealing renal tubular cells and inflammatory cells.
In some renal transplant patients, the necessary use of immunosuppressant medications has the side-effect of allowing the virus to replicate within the graft, a disease called BK nephropathy.
It is thought that 1-10% of renal transplant patients progress to BK virus nephropathy (BKVN) and up to 80% of these patients are reported to have lost their grafts. The onset of nephritis can occur as early as several days post-transplant to as late as 5 years.
It is not known how this virus is transmitted. It is known, however, that the virus is spread from person to person, and not from an animal source. It has been suggested that this virus may be transmitted through respiratory fluids or urine, since infected individuals periodically excrete virus in the urine.
A survey of 400 healthy blood donors was reported as showing that 82% were positive for BK virus.
This virus can be diagnosed by BKV blood & urine testing, in addition to carrying out a biopsy in the kidneys. PCR techniques are often carried out to identify the virus.
A multiplex real-time PCR method for quantification of BK and JC polyomaviruses in renal transplant patients. Rubio L, Pinczewski J, Drachenberg CB, Vera-Sempere FJ, Zhao RY. Diagn Mol Pathol. 2010 Jun;19(2):105-11. PMID: 20502188
Clinicopathologic analysis of patients with BK viruria and rejection-like graft dysfunction. Batal I, Franco ZM, Shapiro R, Basu A, Tan H, Kayler L, Zeevi A, Morgan C, Randhawa P. Hum Pathol. 2009 Apr 20. PMID: 19386348
Galan A, Rauch CA, Otis CN. Fatal BK polyoma viral pneumonia associated with immunosuppression. Hum Pathol. 2005 Sep;36(9):1031-4. PMID: 16153469
Hirsch HH, Steiger J. Polyomavirus BK. Lancet Infect Dis. 2003 Oct;3(10):611-23. PMID: 14522260