Summary:Hemorrhagic cystitis (HC) is a common complication following high-dose chemotherapy and bone marrow transplantation, and the treatment of virus-associated HC remains to be optimized. This is the first report on the successful use of cidofovir in a patient with HC and polyoma viruria concomitant with CMV reactivation after allogeneic BMT. Treatment led to a significant decrease in viruria and to sustained suppression of CMV reactivation. Administered with probenecid and hydration, cidofovir was well tolerated, and there were no side-effects. Bone Marrow Transplantation (2000) 26, 347-350. Keywords: BK virus; hemorrhagic cystitis; cidofovir; CMV reactivation Hemorrhagic cystitis (HC) is a common complication following high-dose chemotherapy and bone marrow transplantation. 1 Although seldom life-threatening, HC may cause significant morbidity. Its cause is attributed to the use of drugs such as oxazaphosphorines and busulfan 1 or to viral infection with adeno-2 and polyomaviruses, 3 but is still not definitively clear.The treatment of virus-associated HC remains to be optimized. Besides hydration and forced diuresis, there is no widely accepted treatment. 1 There have been attempts made with antiviral medication 4 as well as anti-inflammatory local therapy. 5 Cidofovir is a cytidine nucleoside analogue recently licensed as an intravenous treatment for CMV retinitis in AIDS patients. It is, however, also the most active of several compounds tested against polyomaviruses such as BK virus and JC virus, respectively. 6 Here, we describe the successful use of cidofovir in a patient with reactivated CMV infection and severe HC associated with polyomavirus (BK). Case reportA 54-year-old Caucasian man with CML was transplanted in second chronic phase with bone marrow from an unrelated HLA-identical donor. Pretransplant therapy included fludarabine 30 mg/m 2 i.v. once daily for 6 consecutive days (total dose 180 mg/m 2 ), busulphan 4 mg/kg p.o. in divided doses daily for 2 days (total dose 8 mg/kg), and rabbit antithymocyte globuline (Fresenius) 10 mg/kg i.v. once daily for 4 consecutive days (total dose 40 mg/kg). 7 CMV serology (IgG) of both donor and recipient was positive. GVHD prophylaxis consisted of cyclosporin A from day −1 onwards. On day +5, the patient observed some small blood clots in his urine, which were attributed to concurrent thrombocytopenia. The next day, the hematuria resolved spontaneously and was not noticed until day +16, when a second episode of microhematuria was seen lasting for 3 days. Acute grade II GVHD of the skin developed on day +19 and was treated with methylprednisolone (starting at 2 mg/kg daily p.o. in two doses with subsequent taper). GVHD resolved uneventfully within 3 weeks. Engraftment of leukocytes (Ͼ1000/ l) was noted on day +14, and of platelets (Ͼ25 000/ l) on day +16, respectively.On day +42, however, severe macrohematuria recurred together with severe dysuria and voiding frequency of 15 times a day. On ultrasound examination, the patient showed urinary retention as we...