Persistent clonal chromosomal abnormalities in a chronic myeloid leukemia patient

Clonal cytogenetic abnormalities (CCA) in Philadelphia chromosome (Ph)-negative cells have been reported in a small population of adult chronic myelogenous leukemia (CML) patients during the clinical course, but CCA in pediatric CML patients are rarely reported. We herein report the case of an 8-year-old boy from the onset of CML. Although he had relapse after unrelated bone marrow transplantation when 9 years old, he has since been in complete molecular response on imatinib mesylate treatment. Surprisingly, various CCA have been observed in this patient, including several reciprocal chromosomal translocations in Ph-negative cells for >12 years. Although dysplasia in the bone marrow cells was identified, no overt transformation to myelodysplastic syndrome or acute myeloid leukemia has been observed. The cause of the CCA remains unknown in this patient, and careful observation is required.