The First Reported Case of Allogenic Hematopoietic Stem Cell Transplantation for CML Blast Phase (Monocytic Lineage) in the Tyrosine Kinase Inhibitor Era

Chronic myeloid leukemia (CML) blast phase (monocytic lineage) is extremely rare. A 39-year-old Japanese man was diagnosed with CML blast phase (monocytic lineage). T315I mutation was positive, ponatinib was initially started, and then, allogenic hematopoietic stem cell transplantation (allo-HSCT) was performed. Seven days after allo-HSCT, hyper-acute graft-versus-host disease developed, and medial temporal lobe encephalitis emerged 24 days after allo-HSCT. He was alive for over 1 year after allo-HSCT. This is the first case report of HSCT for CML blast phase (monocytic lineage) in tyrosine kinase inhibitor era. Further cases should be documented for effective treatment regimen and analysis of clinical features.