Malignant clonal disorder of haematopoietic stem cells.
At presentation, one third of patients may be asymptomatic; if present, symptoms typically include malaise, fever, weight loss, abdominal discomfort, and night sweats.
Splenomegaly is the most common physical finding; nearly all patients will have elevated WBC count.
Presence of Philadelphia chromosome and /or molecular demonstration of the BCR-ABL transcript confirms diagnosis.
Treatment with a BCR-ABL tyrosine kinase inhibitor gives long-term remission without significant adverse events in most patients.
Chronic myelogenous leukaemia (CML) is a malignant clonal disorder of the haematopoietic stem cell that results in marked myeloid hyperplasia of the bone marrow.  Dysregulation of haematopoiesis arises due to a BCR-ABL fusion gene that causes an abnormal expansion of myeloid cells in the bone marrow and peripheral blood. The 'chronic phase' of the disease may transform to an 'accelerated' or 'blast' phase in 5% to 10% of patients despite treatment with a tyrosine kinase inhibitor, the latter resulting in acute myeloid or acute lymphoblastic leukaemia.  
Honorary Consultant in Haematology
The Christie NHS Foundation Trust
TS has received travel support and speaker expenses from Novartis, and has served as a consultant to Novartis for development of drugs for indications other than CML.
Dr Tim Somervaille would like to gratefully acknowledge Dr Han Myint and Dr Robert Chen, the previous contributors to this monograph. HM sits on the advisory board of Novartis and Bristol-Myers Squibb, and also does speaking engagements on their behalf. RC declares that he has no competing interests.
Section of Hematology and Oncology
Department of Internal Medicine
Wake Forest University Baptist Medical Center
RC declares that she has no competing interests.
Professor of Haematology
Royal Liverpool University Hospital
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