Chronic myeloid leukemia with two rare fusion gene transcripts of atypical BCR::ABL: A case report and literature review

Rationale: Imatinib is a standard treatment for Philadelphia (Ph) chromosome-positive chronic myeloid leukemia (CML), but its efficacy in rare BCR::ABL variants is underexplored. Patient concerns: A 67-year-old woman was admitted to the Second Affiliated Hospital of Xian Jiaotong University in March 2022 due to elevated white blood cells. Diagnosis: Karyotype analysis revealed clonal abnormalities involving the variant t(9;22) and positive results for atypical BCR::ABL variants (e14a3 and e13a3). The clinical diagnosis was CML, chronic phase, Ph+, with rare BCR::ABL-e13a3- and BCR::ABL-e14a3-positive findings. Intervention: The patient was administered daily imatinib mesylate (400 mg). Outcomes: After 4 weeks, a swift molecular response was observed: BCR::ABL-e13a3 transcript level at 2.82 x 10(-1) (28.24%), and BCR::ABL-e14a3 transcript level at 4.68 x 10(-1) (46.76%). Within 3 months, a complete cytogenetic response was achieved, with a Ph chromosome ratio of 0. Early molecular response was evident as BCR::ABL-e13a3 transcript level reached 5.11 x 10(-3) (0.51%), and BCR::ABL-e14a3 transcript level at 6.26 x 10(-3) (0.63%). The imatinib mesylate treatment continued without significant toxicity. Lessons: This case emphasizes the potential effectiveness of imatinib mesylate in managing rare BCR::ABL fusion gene variants of CML. Screening for these atypical variants is advised for suspected CML patients who test negative for common BCR::ABL fusion gene variants. The presented case underscores the positive outcomes achieved with imatinib treatment for a patient with rare BCR::ABL variants, contributing valuable insights for the management of similar cases. Screening for unusual fusion gene variants should be a consideration in CML diagnosis for comprehensive treatment strategies.