Late onset hemorrhagic cystitis after bone marrow transplanatation is caused by:

After bone marrow transplantation (BMT), early-onset hemorrhagic cystitis is related to drugs in the treatment regimen (e.g., cyclophosphamide, ifosfamide), and late-onset hemorrhagic cystitis is usually due to the polyoma virus BKV or adenovirus type 11. Ref: Harrisons principles of internal medicine, 18th edition, Page: 2275.