[BK virus nephropathy after allogeneic hematopoietic stem cell transplantation: a case report and literature review].

A 20-year-old male patient with T-lymphoblastic lymphoma/leukemia received 9/10 human leukocyte antigen-compatible unrelated peripheral blood stem cell transplantation. He was transplanted with 5.91×10(8) mononuclear cells/kg and 2.88×10(6) CD34(+) cells/kg, and neutrophil engraftment was obtained at +11 days and platelet engraftment at +9 days. After transplantation, he presented with repeatedly increased serum creatinine levels, BK virus (BKV) -associated hemorrhagic cystitis, and BKV viremia. BK virus nephropathy was diagnosed based on renal biopsy and metagenomic next-generation sequencing. After adjusting the immunosuppressant, intravenous immunoglobulin, and donor lymphocyte infusion treatment, the patient's renal function deteriorated progressively, and he eventually died of multiple organ failure at +289 days.