Chronic myeloid leukemia (CML) is a chronic type of leukemia. It’s also called chronic myelogenous leukemia. CML occurs when an abnormal gene allows cancer to spread in your body.

Researchers have discovered many chromosomal mutations that can cause various types of cancer. There is especially strong research linking chromosomal mutations and different types of leukemia.

This article will explore the link between CML and chromosomal mutations.

CML is a type of leukemia that starts in specific cells of your blood marrow called myeloid cells.

Your myeloid cells make red blood cells, platelets, and several types of white blood cells. When you have CML, a genetic change creates an abnormal gene known as BCR-ABL. The BCR-ABL gene causes myeloid cells to grow out of control. The myeloid cells build up in your bone marrow and eventually spread into your bloodstream.

Leukemias are classed as either chronic or acute, depending on how fast they grow and spread. CML is a slow-growing, chronic leukemia.

The cancer cells that CML creates usually mature partially. Because these cells are able to behave enough like healthy white blood cells, it often takes years for any symptoms to develop.

Over time, CML can turn into fast-growing leukemia. At this stage, CML can be difficult to treat.

According to the National Cancer Institute, the 5-year relative survival rate for CML is 70.6 percent. One major factor that influences survival rate is the phase that CML is in at the time of diagnosis. As with most cancers, diagnosis at an early stage makes CML easier to treat.

There are three phases of CML:

  • Chronic phase. The chronic phase of CML can last for several years. In this phase, less than 10 percent of blood and bone marrow cells are cancer cells. Without treatment, the chronic phase can progress to a more aggressive phase.
  • Accelerated phase. In the accelerated phase of CML, about 10 to 19 percent of the blood and bone cells will be cancerous cells.
  • Blast phase. This phase is sometimes called a blast crisis. It happens when more than 20 percent of blood and bone marrow cells are cancerous blast cells. People in this phase often have symptoms such as weight loss, fatigue, fever, and an enlarged spleen. CML can be difficult to control in this phase.

Your chromosomes are long molecules of DNA inside each of the cells in your body. Your DNA contains your genes and tells your cells how to function.

Your DNA was passed on to you by your parents. It’s why physical traits and some health conditions run in families. However, the genes within your DNA can undergo changes during your lifetime. That’s because your body makes billions of new cells every day, and the DNA is copied every time a new cell is made.

Each time a cell divides into two new cells, it has to create a new copy of the DNA in its chromosomes. Most times, this works the way it should. But, sometimes, errors (mutations) can occur within the genes of the DNA when it’s replicated for a new cell.

Cancer has been linked to mutations that can either:

  • turn on genes called oncogenes that accelerate cell growth and division
  • turn off tumor suppressor genes that slow down cell division

When cells in specific parts of your body receive the wrong instructions and grow and divide much faster than they should, it can cause cancer.

The abnormal chromosomes that cause CML have been studied by researchers and are well understood.

We know that CML starts during the cell division process. Every time a cell divides, 23 pairs of chromosomes need to be copied. CML often starts when part of chromosome 9 goes to chromosome 22 and part of chromosome 22 goes to chromosome 9.

This causes chromosome 22 to be shorter than normal and chromosome 9 to be longer than it should be. The shorter chromosome 22 is called the Philadelphia chromosome. About 90 percent of people with CML have the Philadelphia chromosome in their cancer cells.

About the Philadelphia chromosome and BCR-ABL gene

The DNA swapping and the creation of the Philadelphia chromosome lead to the formation of a new gene in the body. When the genes from the short chromosome 22 and genes from the long chromosome 9 combine, they create the cancer-promoting BCR-ABL gene (an oncogene).

The BCR-ABL gene carries instructions that tell the blood cells to make too much of a protein called tyrosine kinase. This protein allows too many white blood cells to form and spread. These cells can grow and divide out of control and overwhelm your other blood cells.

Very rarely, CML occurs in cases with no Philadelphia chromosome or BCR-ABL gene present. There might be undiscovered mutations leading to CML in these cases.

There are no other known causes of CML. However, there are a few risk factors linked to CML. These include:

  • Age. The risk of CML increases as you get older.
  • Sex. Men are slightly more likely to get CML than women.
  • Radiation exposure. Exposure to high amounts of radiation, such as being near a nuclear reactor accident, has been linked to an increased risk of CML.

It’s possible to have CML for years with no symptoms at all. Symptoms that do occur are easy to mistake for other conditions. These typically include:

  • weakness
  • unintentional weight loss
  • loss of appetite
  • feeling full after eating only a small amount
  • easy bleeding
  • night sweats
  • fatigue
  • bone pain
  • a feeling of pain or fullness in your stomach
  • an enlarged spleen you can feel under the left side of your rib cage

If you have symptoms such as unintentional weight loss, easy bleeding, night sweats, or an enlarged spleen, try to see a doctor as soon as you can. Although these symptoms can be caused by other conditions, it’s always best to get them checked out sooner rather than later.

It’s also a good idea to follow up with a doctor if you have any of the other symptoms of CML, especially if these symptoms linger and don’t seem to clear up with self-care or lifestyle measures.

Many types of cancer are linked to changes in the genes that control how cells grow and divide.

Researchers have found a clear link between a specific chromosomal mutation and CML. This occurs when parts of chromosome 22 and chromosome 9 swap during normal cell division.

When this happens, it creates what is called the Philadelphia chromosome that is found in around 90 percent of all people with CML. The Philadelphia chromosome creates the BCR-ABL gene that allows white blood cells to divide and grow faster than they should, which can overwhelm your other blood cells.

Be sure to follow up with a doctor if you have a family history of CML or have any concerns about this type of cancer.