A unique three-way Philadelphia chromosome variant t(4;9;22)(q21;q34;q11.2) in a newly diagnosed patient with chronic phase chronic myeloid leukemia: a case report and review of the literature

• Main Authors: Yuka Torii, Kana Nanjo, Tomomi Toubai, Masashi Hosokawa, Ryo Sato, Akane Yamada, Keiko Aizawa, Masahito Himuro, Satoshi Ito, Masakazu Yamamoto, John Magenau, Ryan Wilcox, Kenichi Ishizawa
• Format: Article
• Language: English
• Published: BMC 2021-05-01
• Series: Journal of Medical Case Reports
• Subjects: t(4;9;22)(q21;Q34; Q11.2); CML; Philadelphia chromosome; Three-way variant
• Online Access: https://doi.org/10.1186/s13256-021-02885-4

Abstract Background Chronic myeloid leukemia is a hematologic malignancy associated with the fusion of two genes: BCR and ABL1. This fusion results from a translocation between chromosomes 9 and 22, which is called the Philadelphia chromosome. Although the Philadelphia chromosome is present in more than 90% of patients with chronic myeloid leukemia, 5–8% of patients with chronic myeloid leukemia show complex variant translocations. Herein, we report a unique case of a three-way translocation variant in chronic phase chronic myeloid leukemia. Case presentation A 40-year-old Asian male who presented with leukocytosis was diagnosed with chronic phase chronic myeloid leukemia. Cytogenetic karyotyping analysis showed 46,XY,t(4;9;22)(q21;q34;q11.2). He was treated with bosutinib and then changed to dasatinib because of intolerance, and MR4.5 (BCR-ABL/ABL ≦ 0.0032%, international scale) was achieved after 17 months of continuous treatment. Conclusion This was the 14th case of t(4;9;22), in particular, a new variant Ph translocation involved in chromosome 4q21 and the first successful case treated with tyrosine kinase inhibitors in the world. We summarize previous case reports regarding three-way variant chromosome translocation, t(4;9;22) and discuss how this rare translocation is linked to prognosis.