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A Tricky Virus

Dr Maggie Ma (President, Hong Kong Society of Transplantation; Vice President, Asian Society of Transplantation)

As transplant patients need long term use of immunosuppressant to prevent rejection, they are more prone to infection than healthy individual. In recently years, more and more kidney transplant patient were found to be infected by a 'tricky virus'. This virus is called BK virus. BK virus is a kind of Polyomavirus that can be find in natural environment.

BK virus will not cause significant infection to immunocompetent individuals. However, when end stage renal failure patients receive kidney transplant and start using immunosuppressant, they are at risk of BK infection and BK virus associated nephropathy (BKVAN).

BKVAN is mostly diagnosed late in advanced stage when irreversible damage has already occurred, leading to graft loss in 40-60% of the affected individuals. Currently, there is no effective antiviral treatment to cure BK infection. Reduction of immunosuppressant is the only proven effective management strategy to manage BK virus infection.

Why BK virus is a 'tricky virus'? This is because the pathological features of BKVAN can mimic acute rejection. If nephrologists treat patients with BKVAN as acute rejection with intense immunosuppressant, this will accelerate the progression of BKVAN.

On the other hand, over aggressive reduction of immunosuppressant may lead to acute rejection. Therefore, meticulous monitoring of viral load and adjustment of immunosuppressant would be needed.

A local study on BK infection showed that the risk of BK infection is highest in the first 2 years after kidney transplant. Routine screening of BK virus infection in early post-transplant year is now recommended to allow on-time detection of BK virus replication and prompt reduction of immunosuppressant at earlier stage of disease.


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