Rapid Transformation to Myeloid Blast Crisis in a Pediatric CML Patient Harboring a Complex t(7;9;22)(q11.23;q34;q11.2) Variant Translocation: A Case Report

ABSTRACT 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 × 10 9 /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.