Abstract
Abstract: We report the case of an 18‐year‐old patient who received an allogeneic bone marrow transplant from an HLA‐identical unrelated donor for a Ph+ acute lymphoblastic leukemia, in his third complete remission. Cyclophosphamide and busulfan were used as conditioning treatment. Acute graft‐versus‐host disease developed on day +9, and the response to adequate treatment (steroids) was favourable. On day +45 the patient developed an acute severe haemorhragic cystitis, and BK polyomavirus was demonstrated in urine samples using electron microscopy and polymerase chain reaction. Urinary symptoms did not improve in spite of palliative treatment, but a response was evident after 2 weeks of cidofovir treatment.