Abstract B004: Chronic Myeloid Leukemia in a 40-Day-Old Infant: Diagnostic Role of Cytogenetics and BCR::ABL1 Detection in Early Identification of Congenital CML

Background: Chronic myeloid leukemia (CML) is extremely rare in neonates and infants. We present a case of a 40-day-old male infant admitted with persistent jaundice and unexplained leukocytosis (41.8×109/L), eventually diagnosed with congenital CML using cytogenetic methods. Methods: Two bone marrow aspirations were performed. The first showed no blast cells. Due to persistent hematologic abnormalities, a second aspiration was done. Cytogenetic analysis revealed the t(9;22)(q34;q11) translocation, indicating the presence of the Philadelphia chromosome. FISH and PCR confirmed the BCR::ABL1 fusion. The myelogram showed 0.8% blasts, preserved granulocytic maturation, suppression of erythropoiesis, and absence of megakaryocytes. Immunophenotyping identified mature hematopoietic cells from all lineages and a population of B-lymphoid precursors. Results: The patient received antibacterial and supportive therapy, with partial improvement. However, the parents declined further management at our center and transferred the child to a foreign facility, where the diagnosis was reconfirmed, and targeted therapy was initiated. Conclusion: This case illustrates the diagnostic challenge of CML in infants, particularly in the absence of typical morphological features such as blasts in the peripheral smear or marrow. It underscores the essential role of integrated molecular and cytogenetic testing—especially detection of the BCR::ABL1 fusion—in establishing a definitive diagnosis. Early molecular identification allows for timely differentiation from other neonatal myeloproliferative disorders and appropriate therapeutic planning. Given the rarity of congenital CML, such reports contribute to the understanding of disease mechanisms, aid in awareness among clinicians, and emphasize the value of early molecular diagnostics in pediatric hematology-oncology. Citation Format: Merinsa Irsalieva, Zhanna Kambarova, Merinsa Irsalieva. Chronic Myeloid Leukemia in a 40-Day-Old Infant: Diagnostic Role of Cytogenetics and BCR::ABL1 Detection in Early Identification of Congenital CML [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Discovery and Innovation in Pediatric Cancer— From Biology to Breakthrough Therapies; 2025 Sep 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_2):Abstract nr B004.