We describe a patient with Down syndrome whose precursor B-cell acute lymphoblastic leukemia cells expressed INPP5D-ABL1 fusion gene that resulted in a reciprocal chromosome translocation t(2;9)(q27;q34). The fusion gene was present as a small subclone in the primary disease but was first identified at relapse when the subclone had expanded into a major clone. At relapse, the patient responded poorly to conventional induction chemotherapy but a transient morphologic remission was achieved after administration of imatinib monotherapy. This case demonstrates a pathway to relapse in a Down syndrome patients with acute lymphoblastic leukemia through a rare fusion event. It highlights the significance of minor subclonal events in therapy resistance and the opportunity provided for targeted therapy.
*Tampere Center for Child Health Research, University of Tampere and Tampere University Hospital
†Laboratory of Clinical Genetics, Fimlab Laboratories, Tampere
‡Laboratory of Molecular Hematology and Pathology, Tyks Laboratory Division, Turku
§Department of Hematology, Hematology Research Unit Helsinki, University of Helsinki and Helsinki University Central Hospital Cancer Center, Helsinki, Finland
The authors declare no conflict of interest.
Reprints: Olli Lohi, MD, PhD, Tampere Center for Child Health Research, University of Tampere and Tampere University Hospital, Tampere 33521, Finland (e-mail: firstname.lastname@example.org).
Received March 15, 2018
Accepted June 25, 2018