A Rare Case of Plasmacytoma-like Post-transplant Lymphoproliferative Disorder in a Pediatric Hematopoietic Stem Cell Transplant Recipient Treated With Daratumumab.

Post-transplant lymphoproliferative disorder (PTLD) is a complication of immunosuppressive therapy following solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT). Although PLTD usually presents as B-cell proliferation, plasmacytoma-like PTLD, a rare subtype of monomorphic PTLD, has been described, mostly in SOT recipients. Only 2 cases of this disease entity have been previously reported in patients after HSCT. While the treatment of choice for PTLD is the reduction of immunosuppression combined with rituximab (anti-CD20 monoclonal antibody), the optimal treatment for PTLD with plasmacellular differentiation, which is often CD20-negative, is unknown. We present a case of monomorphic plasmacytoma-like PTLD in a child who received an allogeneic HSCT for relapsed acute lymphoblastic leukemia. He was successfully treated with a myeloma-based approach using an anti-CD38 monoclonal antibody, daratumumab.