Rapid Transformation to Myeloid Blast Crisis in a Pediatric CML Patient Harboring a Complex...

Chronic myeloid leukemia (CML) in chronic phase (CP) typically follows an indolent course. We report a highly aggressive pediatric case with a discordant presentation. A 10-year-old girl presented with rapidly progressive symptoms and hyperleukocytosis (WBC 448.7 × 10⁹/L). Initial bone marrow examination was morphologically diagnostic for CML-CP (blasts 1%). Conventional cytogenetics revealed a complex three-way translocation, t(7;9;22)(q11.23;q34;q11.2). Despite immediate initiation of a second-generation tyrosine kinase inhibitor (TKI), the disease transformed to myeloid blast crisis (BC) within 1 month. This case demonstrates that complex variant translocations, in the absence of other risk factors by standard evaluation, may identify a subset of CML with exceptionally rapid kinetics and inherent TKI resistance. It underscores the high-risk nature of certain cytogenetic findings, even with classic CP morphology, and highlights the critical prognostic information contained in a basic karyotype. Trial Registration: The authors have confirmed clinical trial registration is not needed for this submission.