Durable molecular remission in a patient with chronic myelogenous leukemia and host-derived hematopoiesis after allogeneic bone marrow transplantation

A 44-year-old woman with Ph-positive CML was treated with TBI, splenic irradiation, Ara-C, and CY. She then received unmanipulated marrow cells from her HLA-identical brother. GVHD prophylaxis was FK506 and MTX. WBC counts reached 1000/μl on day 28 when all metaphases of marrow cells showed 46XY. However, on day 42, 46XX was detected in two of 20 metaphases, and the percentage of cells with female karyotype subsequently increased. On day 519, all metaphases showed female karyotype. BCR-ABL mRNA and Philadelphia chromosome were never detected throughout her post-transplant course. Fluorescence in situ hybridization (FISH) revealed complete recovery of host-derived hematopoiesis in the bone marrow, however, mixed T cell chimerism in the peripheral blood. This suggests that the persistence of donor-derived T cells may prevent disease recurrence through graft-versus-leukemia effect. The patient remains in a molecular complete remission with host-derived hematopoiesis 749 days post-transplant.