BK Virus Infections and Hemorrhagic Cystitis in Allogeneic Hematopoietic Stem Cell Transplant Recipients.

BK virus (BKV) associated with hemorrhagic cystitis (HC) is the most important complication that develops after hematopoietic stem cell transplantation (HSCT) in patients with hematological malignancies. This study aims to investigate BKV infections and HC in pediatric patients after allogeneic hematopoietic stem cell transplantation. Between November 2018 and November 2019, a total of 51 patients between the ages of 11 months and 17 years were included in the study. BKV Bosphore ® v1 quantification kit (Geneworks Anatolia, Turkey) was used for the detection of BKV DNA in urine and blood samples. Among the total of 51 patients, the incidence of BKV infection was found to be 86.3%. Allogeneic HSCT was performed in 40 patients and autologous HSCT in 11 patients. BK viruria and/or viremia were detected in 85% (44) of patients who underwent allogeneic HSCT and in 90% in the autologous group. High-level BK viruria (>107 copies/mL) was found in 41% (9) of 22 patients who were BKV positive before transplantation, while in 27.5% (8) of 29 patients who were BKV negative before transplantation; thus, BKV positivity before transplantation was considered a risk factor for high-level BK viruria. Acute GVHD developed in 6 of 40 patients in the allogeneic group. HC was prevented in 12 (67%) of 18 patients who received preemptive treatment, while HC developed in 6 (33%). HC occurred at a median of 35 days (17-49 days) post-transplant. Despite preemptive treatment, 6 (15%) patients who developed HC associated with BKV were in the allogeneic group but not in the autologous group. Of these patients with HC, 5 received a myeloablative treatment regimen, and 1 patient was given a reduced-intensity treatment regimen. The viral load in urine was found to be 107-9 copies/mL within 2 weeks before the development of HC and has been identified as a prognostic indicator. In conclusion, early diagnosis of viral infections by monitoring BKV viral load in HSCT patients will be effective in preventing the progression of complications such as BKV-associated HC by providing timely initiation of preemptive treatment.