This section explains how chronic myeloid leukaemia (CML) is diagnosed. CML affects the white blood cells called granulocytes (which are part of the myeloid family).
Many people feel shocked and upset when told they have CML. If you need support, call Cancer Council 13 11 20.
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Philadelphia chromosome
Most cells in the human body have 23 pairs of chromosomes. Chromosomes are threadlike structures that contain sets of instructions known as genes.
In nearly all people with CML, chromosome 22 is abnormal and is known as the Philadelphia chromosome.
The Philadelphia chromosome is not inherited and cannot be passed on to your children – it is a genetic change that happens to some people during their lifetime. This chromosome contains the BCR-ABL gene (see diagram below).
BCR-ABL is considered a cancer gene because it is present only in developing leukaemia cells. It switches on one of the proteins of the leukaemia cells, called tyrosine kinase. This protein tells leukaemia cells to grow and multiply. All people with CML are treated with drugs to block tyrosine kinase (see Targeted therapy).
Gene swap
The Philadelphia chromosome is formed when parts of two chromosomes break off and switch places. A gene from chromosome 22, called BCR, and a gene from chromosome 9, called ABL, create the BCR-ABL gene.
→ READ MORE: Tests for chronic myeloid leukaemia (CML)
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Key resource
Download a PDF booklet on this topic.
More resources
Dr Chun Kei Kris Ma, Clinical Haematologist, Western Sydney Local Health District (clinical update); Delphine Eggen, Consumer; Dr Robin Gasiorowski, Staff Specialist, Haematology, Concord Hospital; Karl A Jobburn, Haematology Clinical Nurse Consultant, Liverpool Hospital; Yvonne King, 13 11 20 Consultant, Cancer Council NSW; Heather Mackay, Clinical Nurse Consultant, Westmead Hospital; Jennifer Paton, Consumer.
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