Concurrent chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL) in the same patient is rare and may be overlooked when leukocytosis is attributed to a single process. We report a 44-year-old man with progressive weight loss and back pain who was found to have leukocytosis with neutrophilia, absolute lymphocytosis, eosinophilia, and basophilia. Peripheral blood smear and flow cytometry supported CLL, whereas reverse-transcription polymerase chain reaction and cytogenetics demonstrated e13a2 BCR::ABL1 and t(9;22)(q34;q11.2), confirming concomitant CML in chronic phase. Bone marrow examination showed hypercellularity with granulocytic hyperplasia and nodular lymphoid infiltrates, and fluorescence in situ hybridization detected 13q14.3 deletion in the lymphoid clone. Imatinib 400 mg daily was initiated but was replaced with dasatinib 100 mg daily because of intolerance, with subsequent improvement in tolerability and molecular response of CML. At 14 months of follow-up, the patient remained clinically stable on dasatinib with early molecular response at 3 months and major molecular response at 12 months, while the CLL remained under observation without indication for CLL-directed therapy. This case highlights the diagnostic complexity of synchronous hematologic malignancies and the importance of integrating morphology, immunophenotyping, cytogenetics, and molecular studies to guide management.
Almahmood et al. (2026) studied this question.