JC polyomavirus nephropathy confirmed by using an in-house polymerase chain reaction method.

We report the case of an isolated JC virus (JCV) infection, without co-infection by polyoma BK virus (BKV), associated with nephropathy 4 years after kidney transplantation. Clinical suspicion followed the observation of a decrease in estimated glomerular filtration rate (eGFR) and a renal allograft biopsy revealing polyomavirus-associated tubulointerstitial nephritis and positivity for SV40. An in-house real-time polymerase chain reaction assay, targeting the presence of JCV and the absence of BKV in biopsy tissue, confirmed diagnosis. Thirteen months after diagnosis, and following therapeutic measures, eGFR remains stable.