Secondary membranous glomerulonephritis associated with recipient residual lymphoma cells after allogeneic bone marrow transplantation

A 29-year-old man with malignant lymphoma developed membranous nephropathy (MN) after allogeneic bone-marrow transplantation (BMT). There had been no obvious findings of graft versus host diseases (GVHD) after BMT, and the dosage of immunosuppressant drugs had not been reduced during this period. At the onset of MN, a few lymphoma cells still remained in the bone marrow; the patient achieved complete remission of MN after the disappearance of the lymphoma cells. In this case it is suggested that immune complexes including antigens expressed by lymphoma cells might induce MN. Therefore, this is a significant case that may reveal an alternative mechanism of the onset of MN related to BMT.