Introduction

Chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasm driven by the BCR::ABL1 fusion gene, which results from the Philadelphia chromosome translocation and leads to constitutive tyrosine kinase activation [1-3]. The introduction of tyrosine kinase inhibitors (TKIs) has transformed CML from a fatal malignancy into a chronic disease with excellent long-term outcomes for many patients [1-3].

CML is predominantly diagnosed in older adults, with a median age at diagnosis of approximately 60-65 years [1-3]. In contrast, adolescents and young adults represent a relatively small proportion of newly diagnosed cases and often present with higher leukocyte counts, larger spleen size, and greater disease burden at diagnosis [4-7]. As survival continues to improve, understanding the long-term clinical course of CML in younger patients has become increasingly important [4,6,7].

Although most patients harbor the classic t(9;22)(q34;q11.2) Philadelphia chromosome, variant Philadelphia chromosome translocations involving additional chromosomes occur in approximately 5-10% of cases [1,8-11]. The prognostic significance of these uncommon rearrangements remains incompletely understood, particularly for rare three-way translocations involving chromosome 6 [8-14].

We report a case of BCR::ABL1-positive chronic-phase CML diagnosed at 24 years of age in a patient harboring a rare variant Philadelphia chromosome t(6;9;22)(q34;q11.2;p21). Nine years after diagnosis, he remained in chronic phase despite persistent disease burden characterized by marked leukocytosis, massive splenomegaly, marrow fibrosis, and persistent BCR::ABL1 positivity.