Description

• Chronic myelogenous leukemia (CML) is a myeloproliferative neoplasm characterized by clonal proliferation of myeloid precursors in the bone marrow with continuing differentiation into mature granulocytes.
• The hallmark of CML is the Philadelphia chromosome (translocation t[9;22]).
• Natural history of the disease evolves in three clinical phases: a chronic phase, an accelerated phase, and a blast phase or crisis (can transform to acute myeloid leukemia [80%] or acute lymphoblastic leukemia [20%]).

Epidemiology

Incidence

• Per year, 1.9 cases/100,000 persons
• Median age at diagnosis: 65 years
• Predominant sex: male > female (1.7:1)

Prevalence
Accounts for 15–20% of adult leukemias

Etiology and Pathophysiology

Philadelphia chromosome is a balanced translocation between BCR (on chromosome 22) and ABL (on chromosome 9) genes t(9;22)(q34;q11). This fusion gene, BCR-ABL, codes for an abnormal, constitutively active tyrosine kinase that affects numerous signal transduction pathways, resulting in uncontrolled cell proliferation and reduced apoptosis.

Genetics
Acquired genomic changes

Risk Factors

Ionizing radiation exposure (uncommon)