A related donor and reduced intensity conditioning reduces the risk of development of BK virus-positive haemorrhagic cystitis in allogeneic haematopoetic stem cell-transplanted patients.

The significance of the BK virus (BKV) and possible co-factors for the development of late onset haemorrhagic cystitis (HC) in allogeneic haematopoetic stem cell (HSCT)-transplanted patients is reviewed. BKV-associated HC causes significant morbidity and mortality in HSCT patients, however, BK-viruria cannot distinguish patients at risk of HC, since it is observed in patients with and without HC. Several studies have therefore attempted to identify co-factors for the development of HC. Acute graft versus host disease was in the past, though less so recently, reported to correlate to the incidence of HC. However, patients who had received grafts from unrelated donors (URD) and had had full conditioning prior to HSCT were shown to have an increased risk of HC, compared to patients who had received HSCT from a related donor (RD) or patients who had received reduced intensity conditioning. In conclusion, HSCT patients with BK-viruria, an URD and receiving full conditioning have an increased risk of developing HC.