Persistence of various chromosomal aberrations in recipient cells during complete remission after bone marrow transplantation followed by graft rejection

A 16-year-old boy in a second remission of acute lymphoblastic leukemia (ALL) had undergone transplantation of bone marrow from an unrelated donor. The conditioning regimen consisted of high-dose cytarabine, etoposide and 12 Gy of total-body irradiation. Although the donor marrow was rejected, hematopoiesis by the recipient himself recovered and he has remained in complete remission for more than 8 years after stem cell transplantation (SCT). Bone marrow karyotype analysis 1 month after SCT showed random chromosomal aberrations. Although complete remission was maintained, various chromosomal aberrations were detected in marrow cells, and in peripheral blood cells under phytohemagglutinin stimulation over 8 years. Moreover, a clone including del(20)(q11) appeared in marrow cells 7 months after SCT and thereafter was also detected 5 years later in the peripheral blood. This persistence of various chromosomal aberrations and a stable clone without evolution to myelodysplastic syndrome or leukemia support the multi step theory of leukemogenesis.