P-313: Plasmacytoma-like Posttransplant Lymphoproliferative Disorder in a Young Kidney Transplant Recipient

Introduction: Post-transplant lymphoproliferative disorder (PTLD) is a group of lymphoid or plasmacytic proliferations that can occur in transplant recipients as a result of immunosuppression, often driven by the Epstein Barr virus (EBV). While PTLD usually originates from B-cells and resembles B-cell lymphomas, it can exceptionally present as a plasmacytic process resembling multiple myeloma. This report describes a rare case of plasmacytoma-like PTLD in a young kidney transplant recipient.

Methods: Case report

Results: A 23-year-old man who received a kidney transplant in 2003 for perinatal asphyxia complicated by cortical necrosis, was on chronic immunosuppression with methylprednisolone, tacrolimus and azathioprine. He presented diarrhea for several months. Following an episode of acute allograft dysfunction, a urinary tract ultrasound revealed numerous mesenteric and retroperitoneal enlarged lymph node with compression of the left iliac vein. A PET scan confirmed the multiple mesenteric adenomegalia and the presence of hypermetabolic adenopathies in the right cervical region. Further investigations demonstrated a positive blood PCR for EBV ( >3,000 copies/mL), elevated kappa free light chain M-protein (924 mg/l) with an abnormal kappa/lambda ratio (55), with 5-10% abnormal plasma cells in the bone marrow biopsy. A cervical lymph node biopsy showed a plasmacytoma-like PTLD with kappa monotypia. Epstein-Barr encoding region (EBER) in situ hybridization was negative. A colonoscopy was performed due to diarrhea, and colonic biopsies confirmed the presence of the plasmacytoma-like PTLD also in the colon. Treatment included reduction of immunosuppression by discontinuing azathioprine, followed by 8 cycles of bortezomib – dexamethasone and 9 cycles of rituximab, based on CD20-positive cells as part of the population, resulting in complete hematologic and metabolic remission on PET scan, with diarrhea resolution. Notably, we did not use daratumumab as it is not reimbursed in Belgium for this indication. Intensive chemotherapy with melphalan followed by autologous hematopoietic stem cell transplantation was initially planned based on the rare cases reported in the literature, but had to be postponed due to severe myocarditis, likely related to COVID-19 infectious complications. After a follow-up of 21 months, the patient is still in complete metabolic response.

Conclusions:
This case highlights a rare occurrence of plasmacytoma-like PTLD in a young renal transplant recipient. Treatment recommendations are based on a limited number of case series. Effective management has included reduction of immunosuppression and targeted chemotherapy. Despite advances in the treatment of multiple myeloma with immunomodulatory agents and proteasome inhibitors, there is minimal data on their use in PTLD, leaving clinicians with limited guidance on prognosis and treatment. This case highlights the critical need for continued vigilance and personalized care strategies to manage rare post-transplant complications.