Volunteer unrelated donor cell‐derived acute myeloid leukemia with RUNX1‐RUNX1T1

A 15‐year‐old male was diagnosed with acute myeloid leukemia with t(6;9)(p23;q34), a chimeric DEK‐NUP214 fusion gene. He underwent allogeneic bone marrow transplantation (allo‐BMT) from an unrelated volunteer donor at first molecular remission. Approximately 5 years after allo‐BMT, multiple bone marrow aspirations showed increased blasts to 63%, which were positive for myeloperoxidase, CD13, CD33, CD56, and CD34. Surprisingly, t(8;21)(q22;q22.1), a chimeric RUNX1‐RUNX1T1 (not DEK‐NUP214) fusion gene, was detected with full donor chimerism. To our best knowledge, this is the first case of a volunteer unrelated donor cell‐derived acute myeloid leukemia harboring a chimeric RUNX1‐RUNX1T1 fusion gene.