The first case of acute unilateral pan-ureteritis caused by BK polyomavirus in an allogeneic stem cell transplant patient.

Several cases of ureteral obstruction have been reported in stem cell transplant (SCT) patients; however, they were bilateral and concomitant with or preceded by hemorrhagic cystitis. We describe, to our knowledge, a first case of acute unilateral pan-ureteritis caused by BK polyomavirus (BKPyV) in an SCT patient. This case may represent an early phase of BKPyV reactivation. BKPyV infection should be considered as a potential cause of acute unilateral ureteritis even among SCT recipients.