Chronic myeloid leukemia (CML), also known as chronic myelogenous leukemia, is a type of cancer. It starts in blood-forming cells within the bone marrow, creating leukemia cells. These cells transfer to the blood. Over time, they may also settle in other parts of the body, including organs such as the spleen.

People can inherit mutations in their DNA that may increase cancer risk in certain types of cancer, but not in CML. Rather, mutations that cause this cancer develop over a person’s lifetime.

The key difference between chronic and acute myeloid leukemia lies in how the cells mature. In CML, the cancer cells do not fully mature. Instead, they live for longer, crowding out healthy cells from the body. This means that while CML can take longer to cause problems for a person, it is more challenging to cure.

This article takes a closer look at whether CML is hereditary, the risk factors that increase the chances of developing CML, its symptoms, and available treatment.

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According to the American Cancer Society (ACS), people can inherit DNA mutations from a parent that can increase their risk of getting certain types of cancer. However, it states that these mutations cannot cause CML. Instead, the DNA mutations linked to CML occur over a person’s lifetime, rather than being present from birth.

The Genetic and Rare Diseases Information Center confirms this, stating that while CML results from a certain abnormal chromosome, it is not an inherited disease.

Most cases of CML occur when DNA moves between two chromosomes — chromosomes 9 and 22. This is called a translocation. It causes a shorter chromosome to develop, called the Philadelphia chromosome, also known as BCR-ABL1. According to the ACS, this chromosome is found in almost all people with CML.

The Leukemia & Lymphoma Society (LLS) notes a series of risk factors that may increase a person’s risk for developing CML. They include:

  • Sex: CML is slightly more common in males.
  • Age: The risk of developing CML increases with age.
  • Exposure to radiation: People exposed to very high doses of radiation are at a higher risk of developing CML. This does not include radiation from dental examinations or medical procedures.

The ACS says there are no other proven risk factors for developing CML and that it does not develop in response to lifestyle factors, such as diet or smoking. Nor is it caused by infections or exposure to certain chemicals.

As it is a slow-developing disease, many people with CML have no initial signs or symptoms. The LLS says that doctors often diagnose the disease after a routine physical exam or blood test.

When symptoms do develop, they tend to be gradual and may include:

  • muscle fatigue and weakness
  • shortness of breath during physical exercise
  • fever
  • bone pain
  • weight loss
  • pain or feelings of fullness below the ribs on the left side of the body — signs of an enlarged spleen
  • night sweats
  • excessive bruising or bleeding

The most common sign of CML that doctors will look for is too many white blood cells in the blood. Sometimes, people with CML also have low numbers of red blood cells or platelets in the blood.

Treatment for CML may depend on the phase of their disease. There are three phases of CML:

  • chronic
  • accelerated
  • blast

Doctors diagnose the phase by considering several factors, including:

  • immature white blood cells (blasts) present in the blood or bone marrow
  • other types of cells present, such as basophils and promyelocytes
  • platelet counts in the blood
  • chromosomal changes in leukemia cells

An oncologist may recommend one of the following treatments depending on what phase a person with CML is in:

When assessing a person’s outlook with CML, doctors will consider several factors that can affect how the disease may progress. Certain factors negatively impact the survival rate, such as:

  • being at the accelerated or blast phase
  • having an enlarged spleen
  • having bone damage caused by leukemia
  • increased number of eosinophils and basophils — types of white blood cells
  • very high or very low platelet counts
  • being 60 or older
  • having multiple chromosomal changes in CML cells

Historically, doctors have used two systems — the Sokal system and the Euro score — to assess these factors and provide a score that describes a person’s outlook. However, experts have not yet adapted these models to include results from TKI therapy.

Research is ongoing to establish how the system may include TKI therapy. Meanwhile, a 2021 study found that another type of European scoring system — ELTS — was more accurate in predicting the outlook for people receiving TKI therapy compared with Sokal.

Doctors do not consider CML to be a hereditary disease. Most cases of CML occur when DNA moves between two chromosomes, creating an abnormal gene.

Being male, being older, and having exposure to radiation increases the risk of developing CML.

Symptoms may take a long time to develop but can include fatigue, weight loss, and bone pain. Treatment may depend on what stage a person’s CML is at, as does the outlook for survival.