All the cells in our body carry genetic material which determines how each cell will function. This genetic material is made up of genes which are stored on 23 pairs of chromosomes. Each pair of chromosomes is numbered, 1 to 22, with the last two chromosomes being the sex chromosomes X and Y.
In about 6 out of 10 cases of acute myeloid leukaemia [AML] doctors can recognise abnormal changes in the chromosomes of the leukaemic white blood cells.
One such pattern is called a complex karyotype. A karyotype is just the description of all the chromosomes in a particular cell. A complex karyotype means that there are several different genetic changes present. These can include:
- deletions: where part of one or more of the chromosomes is missing
- duplications: where part of one or more chromosomes is repeated of pieces of chromosome
- translocations: where pieces are swapped from one chromosome to another.
These changes interfere with the processes that control the development of white blood cells. This leads to the uncontrolled growth of the leukaemia and also prevents the cells growing into normal healthy white cells.
About 1 in 20 people with AML have a complex karyotype. They are often in an older age group and may have previously received chemotherapy for other reasons. Often they may had a blood condition called myelodysplasia before the development of their AML.
People with AML and a complex karyotype tend to respond less well to chemotherapy. Their remission rates are worse and their survival rates may be less good than with some other types of AML . Because of this people with the complex karyotype of AML may be considered for stem cell transplantation at a relatively early stage of their treatment.