BK Virus Infection in Pediatric Renal Transplantation

Background. Polyomavirus BK (BKV) is a common complication after renal transplantation and an important cause of graft loss. The purpose of this study was to determine the incidence of BKV infection (viremia) in our population and to describe clinical features, global outcomes, and potential correlations with clinical or epidemiologic factors. Methods. This retrospective single-center study included 84 pediatric recipients of kidney transplantation from January 2006 to September 2012. BKV infection screening consisted of periodic determination of decoy cells in urine samples, confirmed by means of quantitative polymerase chain reaction test in blood. Results. Twenty-two patients (26%) developed BKV viremia. BKV replication appeared early after renal transplantation (median, 2 months). One-third of patients remained asymptomatic, and 27% presented elevated serum creatinine. Immunosuppression was reduced in 90% of patients, and 83% achieved clearance of viremia within 6 months. There was only 1 case of histologically confirmed BKV nephropathy, which evolved to graft loss despite leflunomide, intravenous immunoglobulins, and mycophenolate discontinuation. Risk of BKV viremia was associated with younger age at transplantation (5.9 y vs 10.9 years; P = .001) and cadaveric donor (relative risk, 3.2; P < .05). BKV infection did not affect short-term renal function and graft survival. Conclusions. BKV viremia is very common in the pediatric renal transplant population, especially in younger children and in those receiving a kidney from cadaveric donors. It develops in the 1st months after transplantation. Reduction of immunosuppression seems to be a good therapeutic option, with high rates of clearance of the infection, although the only patient with confirmed BKV nephropathy had poor outcome.