Abstract
Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder included in the broader diagnostic category of myeloproliferative neoplasms, associated with fusion by BCR gene at chromosome 22q11 to ABL1 gene at chromosome 9q34 with the formation of the Philadelphia (Ph) chromosome. In 2–10% of CML cases, the fusion gene arises in connection with a variant translocation, involving chromosomes 9, 22, and one or more different chromosomes; consequently, the Ph chromosome could be masked within a complex chromosome rearrangement. In cases with variant Ph translocation a deletion on der(9) may be more frequently observed than in cases with the classical one. Herein we describe a novel case of CML with complex variant Ph translocation involving chromosomes 9, 12, and 22. We present the hematologic response and cytogenetic response after Imatinib treatment. We also speculated the mechanism which had originated the chromosome rearrangement.
Highlights
Chronic myeloid leukemia (CML) is a hematopoietic stem cell disease included in the broader diagnostic category of myeloproliferative neoplasms [1] that is characterized by neoplastic overproduction of mainly granulocytes
CML is consistently associated with fusion by chromosome translocation of the breakpoint cluster region gene (BCR) at chromosome 22q11 to the Abelson gene (ABL1) at chromosome 9q34
We describe a patient with CML associated with a novel cryptic complex variant t(9;22), involving chromosome 12 besides chromosomes 9 and 22, which was unmasked and characterized by Reverse-transcription quantitative polymerase chain reaction (RT-PCR) and FISH analyses
Summary
Chronic myeloid leukemia (CML) is a hematopoietic stem cell disease included in the broader diagnostic category of myeloproliferative neoplasms [1] that is characterized by neoplastic overproduction of mainly granulocytes. CML is consistently associated with fusion by chromosome translocation of the breakpoint cluster region gene (BCR) at chromosome 22q11 to the Abelson gene (ABL1) at chromosome 9q34. This fusion gene BCR/ABL1 encodes for an oncoprotein (P210, more rarely P190 or P230) with a strong constitutive activated tyrosine kinase activity inducing several downstream signals causing the transformation of hemopoietic stem cells [2]. Two variant subgroups have been recognized: the simple variant group with the 22q segment translocated on chromosome other than 9 and the complex variant translocation involving chromosomes 9, 22, and one or more additional chromosome/s. We describe a novel CML case with complex variant Ph translocation involving chromosomes 9, 12, and 22. We evaluated the response to the Imatinib treatment and speculated the molecular events underlying this chromosome rearrangement
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