A Rare Case of Chronic Lymphocytic Leukemia and Chronic Myeloid Leukemia in an Elderly Patient: A Case Report

ABSTRACT Chronic Lymphocytic Leukemia (CLL) and Chronic Myeloid Leukemia (CML) are two distinct hematological malignancies with different pathophysiologies and clinical courses. While each is relatively common in the elderly population, their simultaneous occurrence in a single patient is exceptionally rare and poses diagnostic and therapeutic challenges. We present the case of a 79‐year‐old male who was evaluated for progressive fatigue, weight loss, and marked leukocytosis. Laboratory investigations, peripheral blood smear, flow cytometry, and molecular studies were utilized to establish the diagnosis. Initial findings revealed extreme leukocytosis, anemia, and elevated LDH. Peripheral smear and molecular testing confirmed CML through detection of the BCR::ABL1 fusion gene. Concurrently, flow cytometry identified a clonal B‐cell population positive for CD5, CD19, and CD20, consistent with CLL. Imaging showed splenomegaly and pathologic lymphadenopathy. The patient was treated with imatinib and hydroxyurea, resulting in normalization of white blood cell count, though anemia and thrombocytopenia persisted. This case highlights a rare synchronous diagnosis of CML and CLL in an elderly patient. The comprehensive diagnostic evaluation was critical in establishing the dual pathology. The case underscores the need for heightened clinical suspicion in atypical presentations and contributes to the limited body of knowledge on coexistent myeloid and lymphoid malignancies.