Transformation of Severe Aplastic Anemia into Donor Cell Leukemia after Allogeneic Hematopoietic Stem Cell Transplantation: A Rare Case Report.

BACKGROUND Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important treatment for severe aplastic anemia (SAA). It is known that SAA can evolve into malignant clonal diseases, such as acute myeloblastic leukemia (AML) or myelodysplastic syndrome. However, the transformation of SAA into AML after allo-HSCT is a rare phenomenon. Here, we report a case of SAA transformed into AML after patient received human leucocyte antigen (HLA)-matched sibling peripheral blood stem cell transplantation. CASE REPORT A 51-year-old female patient presented with petechiae and fatigue and received a diagnosis of idiopathic SAA. The immunosuppressive therapy combined with umbilical cord blood transplantation failed for this patient. Then, she received HLA-matched sibling allogeneic peripheral blood stem cell transplantation (allo-PBSCT). However, 445 days after allo-PBSCT, the patient had a diagnosis of AML by bone marrow puncture. Donor-recipient chimerism monitoring and cytogenetic analysis confirmed that the leukemia was donor cell origin. Notably, a new HOXA11 mutation was detected in the peripheral blood of the patient after transplantation by whole-exome sequencing, which was the same gene mutation detected in the donor. The patient received 1 cycle of induction chemotherapy with azacytidine and achieved complete remission. However, the leukemia relapsed after 2 cycles of consolidation chemotherapy. Unfortunately, the patient died of leukemia progression 575 days after allo-HSCT. CONCLUSIONS The mechanism of how normal donor hematopoietic cells transform to leukemia in the host remains unclear. Donor cell leukemia provides a unique opportunity to examine genetic variations in donors and hosts with regards to the progression to malignancy.