CML is caused by a chromosomal translocation between chromosomes 9 and 22 (‘Philadelphia chromosome’) in haematopoietic stem cells, which yields a constitutively active kinase (BCR-ABL1) that drives the uncontrolled cell growth. 




Symptoms of CML can include the following:


  • Elevated level of white blood cells (leukocytes)
  • Enlarged spleen (possibly leading to loss of appetite)
  • Weight loss
  • Enlarged liver
  • Diarrhoea
  • Fatigue
  • Reduction in physical and mental abilities
  • Slight fever
  • Night sweats

The advanced stage of the disease may involve a blast crisis, which is characterised by an increase in the blast count in the bone marrow or peripheral blood or by the development of leukaemic infiltrates in the soft tissue or the skin.




Most patients are diagnosed with a blood test (complete blood count) during a routine check-up in which white blood cell counts are elevated. The diagnosis is confirmed by identification of the Philadelphia chromosome, of 22q or BCR-ABL1 transcripts or of both in the peripheral blood or bone marrow cells.


The recognition of progression of the disease from the chronic to the blast phase is of significance for prognosis and treatment. Immunocytology using flow cytometry and histochemistry permits precise analysis of the immature cells and differentiation between myeloid and lymphoid blast crisis.




A. Hochhaus, S. Saussele, G. Rosti, F.-X. Mahon, J. J. W. M. Janssen, H. Hjorth-Hansen, J. Richter and C. Buske. Chronic Myeloid Leukaemia: ESMO Clinical Practice Guidelines Ann Oncol (2017) 28 (suppl 4): iv41–iv51


A. Hochhaus et al. European LeukemiaNet 2020 recommendations for treating chronic myeloid leukemia. Leukemia (2020) 34:966–984