Chronic myeloid leukemia (CML), also known as chronic myelogenous leukemia, is a myeloproliferative disorder defined by a unique molecular / cytogenetic abnormality in which a balanced translocation between chromosomes 9 and 22 occurs to create the Philadelphia (Ph) chromosome [t(9;22)(q34;q11.2)]. The novel BCR-ABL1 fusion oncogene codes for a protein with tyrosine kinase activity that is constitutively active, leading to activation of many downstream pathways. The result is excessive proliferation and reduced apoptosis of CML cells, causing reduced hematopoiesis.

CML represents about 15%-20% of all leukemias in the United States. Median age at diagnosis is between 50 and 65 years, and there is a slight male predominance.

CML begins in the chronic phase (CP); this may progress to an accelerated phase (AP) and, later, a blast phase (BP), or acute leukemia (> 20% blasts). Approximately 85% of patients will be in CP when they present or are diagnosed.

Related topic: acute myelogenous leukemia