BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Although chronic myelogenous leukemia (CML) is the first example of a leukemia linked to a single cytogenetic and molecular lesion (the chimeric BCR-ABL protein with constitutive tyrosine kinase activity resulting from the t(9;22) translocation), little is known regarding putative inherited factors associated with the risk of developing this disease.