Intravascular Large B-Cell Lymphoma After Kidney Transplantation: A Rare Form of Post-Transplant Lymphoproliferative Disorder.

Intravascular large B-cell lymphoma (IVLBCL) is an extremely rare type of diffuse large B-cell lymphoma characterized by the selective proliferation of lymphoma cells within the lumina of vessels. Here, we report a case of IVLBCL that developed after living-donor kidney transplantation. A Japanese man in his 60s had undergone living-donor kidney transplantation 4.5 years earlier. He was referred to our hospital with a 2-month history of general fatigue and loss of appetite. On admission, blood tests revealed anemia, hypoalbuminemia, and hyponatremia, while renal function remained within the normal range. Thrombocytopenia emerged during hospitalization. Imaging studies detected no tumorous or inflammatory lesions. Bone marrow biopsy demonstrated hypocellular marrow, while random skin biopsy revealed CD20-positive large atypical lymphocytes within the vascular lumina. These findings fulfilled the diagnostic criteria for IVLBCL. Following the diagnosis, one course of R-CHOP therapy was administered; however, the patient died of multiorgan failure on day 31 after admission. Although IVLBCL after organ transplantation is rare, its clinical manifestations can mimic thrombotic microangiopathy or thrombotic thrombocytopenic syndrome. IVLBCL should be considered a rare but critical differential diagnosis of post-transplant cytopenia and systemic symptoms, even when imaging studies are unrevealing, as delayed diagnosis may result in fatal outcomes.