Relapsed RUNX1-RUNX1T1-positive acute myeloid leukemia with
pseudo-Chediak-Higashi granules and C-MYC amplification
A 7-year-old boy was diagnosed with RUNX1-RUNX1T1-positive acute myeloid
leukemia. Although he achieved complete remission (CR) after
conventional chemotherapy, he experienced relapse 6 months after
completing initial treatment. The cytoplasm of myeloblasts examined at
relapse contained pink giant granules. These myeloperoxidase-positive
granules were considered to be pseudo-Chediak-Higashi (PCH) granules.
Meanwhile, blasts had acquired genetic alterations such as
hypotetraploidy with RUNX1-RUNX1T1 and C-MYC amplification, and a KIT
N822K mutation. The patient underwent cord blood transplantation and
maintains a second CR. A previous report suggests that C-MYC
amplification might be associated with PCH granule formation, and our
case supports this hypothesis.