A mutation conferring resistance to imatinib at the time of diagnosis of chronic myelogenous leukemia.

To the Editor: Acquired resistance to imatinib mesylate caused by kinase-domain mutations is common in patients with chronic myelogenous leukemia who are treated with the drug.1 Until now, such mutations have been reported only at the time of clinically apparent resistance or relapse.2,3 We describe a patient with chronic myelogenous leukemia in whom a minor population of imatinib-resistant cells were present at the time of diagnosis. A 67-year-old man presented in August 2001 (month 0) with chronic-phase chronic myelogenous leukemia. Cytogenetic analysis of bone marrow cells revealed 46,XY,t(9;22;12)(q34;q11;q11) in 35 percent of metaphases and 48,XY,t(9;22;12)(q34;q11;q11),+8,+der(22)(q34;q11) in 65 percent of . . .