Visualizing BK virus nephropathy

A 55-year-old man received a kidney transplantation in June 2008 (diabetic end-stage renal disease). Induction of immunosuppression consisted of basiliximab, methylprednisolone and mycophenolate mofetil. Maintenance therapy consisted of prednisone, mycophenolate mofetil and tacrolimus. In December 2008, a kidney biopsy was performed because of deteriorated kidney function and blood BK virus (BKV) replication (105.9 copies/mL). The biopsy showed prominent lymphocytic interstitial infiltrates. Tubulitis was inconspicuous (Figure 1A). Intranuclear inclusion bodies with ground-glass appearance and peripheral chromatin rimming could be seen in some tubular epithelial cells consistent with BKV infection (Figure 1B). No deposits were identified by immunofluorescence. Immunosuppression was reduced. Ten days after the biopsy, a contrast-enhanced CT scan was performed for intercurrent intestinal discomfort (no specific diagnosis made, with spontaneous recovery). The CT scan showed multiple wedge-shaped areas and streaky zones of lesser enhancement that extended from the papilla to the renal cortex (Figure 2). Ultrasonography performed the same day showed very similar abnormalities. The patient was afebrile. The urine dipstick showed no leucocytes, no red blood cells and no nitrite. The C-reactive protein was 5.5 mg/dL (N