Combination of mesenchymal stem cells and cidofovir for the treatment of BK virus-associated late-onset hemorrhagic cystitis after allogeneic hematopoietic stem cell transplantation: a case report.

This case report describes a 22-year-old female patient who developed refractory grade IV BK virus-associated late-onset hemorrhagic cystitis (HC) on day 69 following haploidentical hematopoietic stem cell transplantation. After conventional stepwise interventions-including bladder irrigation, repeated transcatheter arterial embolization, and endoscopic electrocoagulation-failed to achieve disease control, a combination regimen comprising umbilical cord-derived mesenchymal stem cells (MSCs) and intravenous cidofovir was administered on day 84 post-transplant. Following this combined therapy, the patient's bladder hemorrhage was progressively controlled, dysuria was relieved, and transfusion requirements decreased. Macroscopic hematuria began to decrease on day 98 post-transplant and resolved completely by day 124, accompanied by a marked decline in BK viral load during follow-up. This case suggests that the combination of MSCs and cidofovir may serve as a potential salvage strategy for severe, refractory virus-associated HC and may also offer ancillary benefit in promoting hematopoietic recovery.