Pediatric chronic myeloid leukemia with B-cell lymphoid blast crisis at presentation

Letters to the Editor 151 Fig. 1. Blood film demonstrating chronic myeloid leukemia in lymphoid blast transformation. in beta-thalassemia patients: a single-center experience and a concise review of the literature. Chronic myelogenous leukemia in sickle cell/beta 0-thalassemia. of lymphoma with bone marrow involvement in a boy with beta+ thalassaemia major. Pediatric chronic myeloid leuke-mia with B-cell lymphoid blast crisis at presentation TO THE EDITOR: Chronic Myeloid Leukemia (CML) is a rare hematological malignancy accounting for less than 3% of pediatric and adolescent leukemias, with an annual incidence of approximately 1 per million children and young people aged ＜20 years [1]. The natural history and biology of pediatric CML is similar to those of adult CML and follows a tri-phasic pattern. Approximately 95% of children present with chronic phase CML (CML-CP) and the remainder present in the accelerated phase CML (CML-AP) or in blast crisis (CML-BC) [2]. CML-BC is defined by ＞20% blasts in the marrow or the presence of extra-medullary blast proliferation [3, 4]. Blast transformation of CML is lymphoid in 30% of cases and myeloid in the remaining 70%. We report the case of a 10-year-old boy who presented with a 6-week history of weight loss and left-sided upper abdominal pain. On examination, he was found to have substantial splenomegaly extending into the right iliac fossa. His full blood count showed a hemoglobin level of 6.6 g/dL, a platelet count of 148×10 9 /L, and a total white cell count of 575×10 9 /L. Chromosome analysis showed a t(9;22)(q34;q11) trans-location consistent with a Philadelphia chromosome (Fig. 2A). Interphase fluorescence in situ hybridization (FISH) showed BCR-ABL1 fusion signals in 90% of the nuclei (Fig. 2B). A minor breakpoint cluster region (210 kDa) was confirmed using RT-PCR. In the absence of a documented CML-CP, distinguishing between lymphoid blast crisis of CML and a Philadelphia chromosome-positive ALL can be difficult. A diagnosis of CML in B-cell lymphoid blast crisis rather than de novo precursor B-cell ALL was made because of the concurrent presence of basophilia, a predominance of metamyelocytes and myelocytes, and the p210 BCR-ABL transcript. The patient did not have any additional chromo-somal anomalies associated with advanced phase CML and was negative for IgH rearrangement on FISH analysis. The patient achieved a complete hematological response and a minor cytogenetic response following induction therapy comprising dexamethasone, vincristine, daunorubicin, asparaginase, and imatinib. Nonetheless, he subsequently died of idiopathic pneumonitis after allogeneic stem-cell transplantation. …