BK Virus-Related Haemorrhagic Cystitis in Non-Transplanted Children With Leukaemia.

Background: Although it is well-known in transplant recipients, BK virus (BKV)-related haemorrhagic cystitis (HC) is an unexpected complication in children with leukaemia on standard chemotherapy.

Methods: This retrospective observational study reported non-transplanted children who experienced BKV-related HC during acute lymphoblastic leukaemia (ALL) or acute myeloid leukaemia treatment. Disease status, HC grade, BKV copy number in urine, blood counts, imaging findings, HC treatments and preceding oral mucositis and posterior reversible encephalopathy syndrome (PRES) were evaluated.

Results: Twenty-three children with leukaemia were tested in urine BKV polymerase chain reaction for haematuria aetiology, and BKV was detected in 14 (60.9%). Seven of the patients (50%) had T cell ALL, 10 were 10 years old and older (71.4%) and 11 were male (78.6%). All patients were in the consolidation phase of therapy, and except one, all were in remission during HC. The mean BKV copy number in the urine was 0.443 × 10⁹ ± 0.203 × 10⁹/mL. Four patients (28.6%) had grade I, seven (50.0%) had grade II, and three patients (21.4%) had grade III HC. HC grades were correlated with neutrophil to lymphocyte ratio (r_s = 0.616, p = 0.019). Preceding/concomitant oral mucositis in nine (64.3%) and PRES in the previous 3 months in five patients (35.7%) have been noted.

Conclusions: BKV-related HC is a potential complication of patients with leukaemia during the consolidation phase of treatment. The risk factors of BKV-related HC in children with leukaemia are similar to those of haematopoietic stem cell transplantation recipients.