Philadelphia chromosome-positive chronic myeloid leukemia in a 27-month old toddler: a case report highlighting diagnostic and therapeutic challenges in a resource-limited setting

Chronic myeloid leukemia (CML) is a rare pediatric malignancy, accounting for 2–3% of childhood leukemias, with an incidence of approximately 0.6–1 case per million children annually. Occurrence in children younger than 3 years is exceptionally uncommon. The disease is defined by positive Philadelphia chromosome resulting from BCR::ABL1 fusion gene. A 27-month-old boy presented with a short history of fever and cough. Laboratory evaluation revealed extreme hyperleukocytosis (white blood cell count 315,000/µL) and thrombocytosis. The clinical findings were minimal, with only mild splenomegaly. Bone marrow examination demonstrated marked hypercellularity with myeloid predominance and preserved maturation. Fluorescence in situ hybridization (FISH) confirmed the presence of the BCR::ABL1 fusion gene, establishing chronic-phase CML. Due to limited local availability, molecular testing required a referral to a centralized laboratory. Initial management with hydration, allopurinol, and hydroxyurea resulted in effective cytoreduction. The patient achieved a clinical and substantial early hematologic response over approximately two months of follow-up after initiating imatinib therapy. Philadelphia chromosome-positive CML in children younger than 3 years is exceptionally rare. Early recognition in children with marked leukocytosis despite limited clinical symptoms, followed by molecular confirmation and timely targeted therapy, is essential, while limited access to molecular monitoring remains a challenge in resource-limited settings.