Infectious complications after hematopoietic stem cell transplantation: current status and future perspectives in Korea

Cho, Sung-Yeon; Lee, Hyeon-Jeong; Lee, Dong-Gun

Hemorrhagic cystitis in HSCT recipients can be classified according to the onset time (before vs. after engraftment), and cases occurring within 7 days after transplantation are usually non-infectious. Non-infectious causes include radiotherapy and chemotherapy (e.g., cyclophosphamide, ifosfamide, busulfan, and etoposide), while post-engraftment hemorrhagic cystitis can be caused by virus. Viral reactivation can be accompanied by bladder urothelial damage due to the conditioning regimen. Viral hemorrhagic cystitis can be caused by polyomaviruses (BK and JC viruses), adenovirus, CMV, HSV, and HHV6 [107, 108] . Of these viruses, BK virus (BKV) is the most common; 80% to 90% of adults are BKV seropositive [109] [110] [111] . BKV-associated hemorrhagic cystitis is predominant in allogeneic HSCT patients, and BKV-associated nephropathy in KT patients. Why BKV reactivation manifests as these two major forms in KT and HSCT patients is unclear [112] . The diagnostic criteria defined by the European Conference on Infections in Leukemia (ECIL)-6 comprise the following triad: viral replication (urine BKV > 10 7 copies/mL), symptoms of cystitis, and hematuria of grade II or higher. A blood BKV DNA level of > 10 3-4 copies/mL is reportedly associated with significant viruria. However, a negative plasma viral load does not rule out BKV-associated hemorrhagic cystitis [113] [114] [115] .