[Multiple myeloma treated with haploidentical hematopoietic stem cell transplantation with the administration of post-transplant cyclophosphamide].

We report the case of a 58-year-old woman with multiple myeloma who relapsed after the first autologous peripheral blood stem cell transplantation. She was refractory to new drugs and underwent a haploidentical allogeneic hematopoietic stem cell transplantation (haplo-HSCT) by administering post-transplantation cyclophosphamide (PTCy) after the second autologous peripheral blood stem cell transplantation. Neutrophil and platelet engraftment were achieved on days 22 and 55, respectively. Grade II cutaneous acute graft-versus-host disease was observed, which was resolved by systemic steroid treatment. Post-transplant bone marrow examination confirmed donor chimerism replacement and immunophenotypic complete response, and the patient is alive and disease-free. Although haplo-HSCT using PTCy for multiple myeloma has not been reported in Japan, it could be performed safely. Here, we report our results with literature review.