Transformation from chronic myelogenous leukemia to acute lymphoblastic leukemia in children: A case report Ni Made Dwi Rosmiati a , Delita Prihatni b Corresponding author: dwimadevip@gmail.com a Residency Program, Department of Clinical Pathology, Faculty of Medicine, Padjadjaran University, Dr. Hasan Sadikin AcademicGeneral Hospital, Bandung, Indonesia b Staff in Department of Clinical Pathology, Faculty of Medicine, Padjadjaran University, Dr. Hasan Sadikin Academic General Hospital, Bandung, Indonesia Abstract Chronic Myelogenous Leukemia (CML) is a myeloproliferative neoplasm that can progress into various conditions. Transformation of CML into Acute Lymphoblastic Leukemia (ALL) is rare. An 8-year-old girl is brought to the hospital because of a fever. physical examination revealed hepatosplenomegaly, the patient had a history of bone marrow morphology examination in 2019 chronic phase CML with blast count <10%. In 2021, an assessment of the bone marrow was carried out again, showing a hypocellular picture, no erythropoiesis cells, and only a few granulopoiesis cells were found, and there were no megakaryocytes. Infiltrating lymphoblasts dominate cells in the bone marrow. The transformation of CML to ALL can occur in 5% of children and 40% of adults. Change can occur due to genetic mutations and inadequate treatment. Keywords: Chronic myelogenous leukemia, acute lymphoblastic leukemia, transformation. 1. Introduction Chronic myeloid leukemia is a myeloproliferative neoplasm originating from pluripotent stem cells. The Philadelphia chromosome (Ph) is the result of a translocation between chromosomes 9 and 22, which can be detected in myeloid, erythroid, megakaryocytes, B lymphocytes, and sometimes T lymphocytes. Chronic Myelogenous Leukemia (CML) consists of three phases, namely the chronic phase, acceleration phase, and blast crisis phase. In nearly 85% of patients, CML is chronic phase CML Confirmation of the diagnosis is obtained by identification of the Philadelphia chromosome or the BCR ABL gene or both, in peripheral blood cells or bone marrow (BM) 2. Case A pediatric patient aged 8 years came with complaints of fever 10 days before admission to the hospital. Complaints of fever were felt continuously. Complaints accompanied by bleeding gums. The patient 2019 was diagnosed with Chronic Myeloid Leukemia through a bone marrow puncture examination at Hasan Sadikin Hospital, BCR-ABL has not been tested yet. The patient in this case based on the results of the 2019 bone marrow examination was diagnosed with chronic phase CML because the blast count was < 10%. The patient 3 weeks earlier had been treated at Thamrin Hospital, Jakarta, for 7 days and was given a transfusion of 2 units of Packed Red Cell blood and 6 units of platelet blood. Then the patient was referred to Hasan Sadikin Hospital RSHS) for further treatment. Patients routinely take hydroxyurea 1x1 tablet/day since the 248 www.ijrp.org IJRP 2022, 113(1), 248-252; doi:.10.47119/IJRP10011311120214142