Leucine replaced by methionine at 273 position in chronic myeloid leukemia: Knowns and unknowns…

Chronic myeloid leukemia is a clonal bone marrow stem cell disorder characterized by the presence of Philadelphia chromosome t(9;22)(q34;q11) leading to fusion oncogene BCR-ABL. Tyrosine kinase inhibitors (TKIs) act by competitively inhibiting BCR-ABL oncoprotein with significant response rates. However, up to 30% of patients fail to achieve complete cytogenetic remission on 1^st line TKI imatinib, one of the reasons being mutations in BCR-ABL kinase domain leading to imatinib resistance. Over 80 such mutations have been documented in the literature; however, some of the rare mutations still remain to be studied for their impact in development of resistance and their responsiveness to currently available therapeutic options. Here, we report one such case of a rare mutation leucine replaced by methionine at 273 position and its clinical implications.