A Rare Case of p190 BCR-ABL Chronic Myeloid Leukemia With a Very Good Response to Tyrosine Kinase Inhibitors.

The oncoprotein BCR-ABL has distinct fusion proteins generated from the Philadelphia chromosome translocation, depending on the site of the breakpoint on chromosome 22. The p210 is the hallmark of chronic myeloid leukemia. Only 1% - 2% of patients with chronic myeloid leukemia (CML) demonstrate p190 BCR-ABL. Imatinib mesylate, a tyrosine kinase inhibitor (TKI), specifically targets BCR-ABL, which brought a revolutionary era to the treatment of CML. Although the efficacy of imatinib is widely known, resistance to it has become a pressing challenge in the treatment of CML. CML patients harboring atypical e1a2 transcript (referred to as p190 BCR-ABL) show a poor and short-lived response to first-generation TKI therapy. Patients with p190 BCR-ABL CML should be identified as high-risk patients from the beginning to allow the best chance of a deep molecular response. These patients must be closely monitored during TKI therapy and should be treated upfront with a second-generation TKI. We report a case of p190 BCR-ABL CML with a good response to second-generation TKI.