BK Polyomavirus Viremia and Viruria Frequency in Children Who are Receiving Immunosuppressive Treatment due to Kidney Diseases

Background BK polyomavirus (BKPyV) is an important cause of nephropathy, graft dysfunction and loss in patients receiving immunosuppressive therapy after solid organ transplantation, especially kidney transplantation. However, the full spectrum of BKPyV-related kidney diseases in immunocompromised patients remains unclear. The aim of our study was to evaluate the frequency of BKPyV-DNA in blood and urine in patients who received immunosuppressive treatment due to kidney diseases other than kidney transplantation and to compare healthy controls. Methods A total of 46 (25 female) children, who were using immunosuppressive treatment and were under follow-up due to kidney diseases at the pediatric nephrology outpatient clinic and 28 (13 female) healthy controls, were included in the study. BKPyV quantitation was performed in urine and serum samples by real time polymerase chain reaction (PCR). Results Patient group and control group mean ages were 11.3±4.6 and 9.92±4.5 years respectively. There was no statistical difference between the patient and control groups regarding age and sex distribution (p>0.05). Twenty-four (52.2%) patients were receiving methylprednisolone, 14 (30.4%) patients were receiving dual, 1 (2.2%) patient was receiving triple immunosupressive therapy and 7 (15.2%) patients were receiving single immunosupressive therapy other than steroid. BKPyV-DNA was detected in the urine samples of 2 (4.35%) patients while there were no BKPyV-DNA positivity in plasma samples. One of these patients was being followed up with the diagnosis of systemic lupus erythematosus (SLE). Until the sample date, she had received methylprednisolon pulses, oral methylprednisolon, intravenosus immunglobulin, intravenousus cyclophosphamide, mycophenolat mofetil and rituximab. The patient’s current treatment was cyclosporin and oral methylprednisolon. The second patient was diagnosed with steroid-dependent nephrotic syndrome. He had recevied cylophosphamid previously and his current treatment was oral methylprednisolon. Remarkably, both patients had a history of cyclophosphamide treatment. There were no positivity in the plasma and urine samples of the healthy control group. Conclusion The use of steroids alone in immunosuppressive therapy does not appear to be an important risk factor for BKPyV reactivation. It does not seem necessary to perform plasma and urine BKPyV-DNA screening in pediatric patients not receiving intensive immunosuppressive therapy. It has been thought that BKPyV reactivation may be more frequent, especially if the underlying disease is SLE or if cyclophosphamide is used as an immunosuppressive, and BKPyV screening may be performed in these patients. The absence of positivity in any patient in our healthy control group suggests that BKV viruria and viremia are very low in healthy children.