CMV reactivation induced BK virus-associated late onset hemorrhagic cystitis after peripheral blood stem cell transplantation

Hemorrhagic cystitis (HC) is a known complication of stem cell transplantat ion. In contrast to early-onset HC that is usually attributed to cyclophosp hamide and occurs within a few days of infusion, late onset HC is associate d with viral infection. In recent years BK virus has emerged as an importan t causative agent. We describe two patients who developed late onset HC (38 and 92 days post transplant) associated with BK viruria concomitant with C MV reactivation and suggest a possible role of CMV in the process of BK vir us DNA replication.