Chronic myeloid leukemia, or chronic myelogenous leukemia, is a type of cancer. It affects parts of the bone marrow that form immune cells, red blood cells, and platelets.

If someone has chronic myeloid leukemia (CML), they get ill frequently as their white blood cells do not work as they should. They may feel tired and weak because of repeat infections. They also may have swelling and pain in places where the cancerous cells build up, such as their lymph nodes, bones and joints, and abdomen.

Doctors do not know what causes CML, but factors such as age and race can affect a person’s likelihood of developing the disease. Treatment options include chemotherapy, stem cell transplants, targeted therapy, and immunotherapy.

According to the American Cancer Society, in the United States, doctors will diagnose 5,150 men and 3,960 women with CML in 2021. The number of child CML cases is far fewer than adults, as the average age at diagnosis is around age 64 years.

This article explores chronic myeloid leukemia, its symptoms, diagnosis, and potential treatments. Finally, it looks at someone’s outlook if they have this condition and where they can find support.

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CML is a type of cancer that starts in blood-forming cells of the bone marrow, called myeloid cells.

The bone marrow contains stem cells that can develop into many different types of cells. These include red blood cells that carry oxygen, white blood cells that fight infection, and platelets that help the blood to clot.

If someone has leukemia, their bone marrow cells begin to behave abnormally. Leukemias are acute or chronic depending on the abnormal cell’s stage of maturity.

CML is a type of chronic leukemia. In these leukemias, the abnormal cells are not completely mature and cannot fight infection as effectively as typical, fully mature white blood cells. These leukemia cells live longer than regular cells, meaning that they build up and overtake normal cells in the bone marrow.

Someone with CML can live for years without problems. But doctors find these forms of leukemia more challenging to cure than acute leukemias.

Doctors also classify leukemias as lymphocytic or myeloid. CML is a myeloid leukemia. The classification depends on the bone marrow cells the cancer originates from. Lymphocytic leukemias develop in the cells that turn into lymphocytes, whereas myeloid leukemias start in early myeloid cells. These cells can become red blood cells, platelet-making cells, or white blood cells other than lymphocytes.

For many individuals, there are no obvious reasons why they develop CML. People cannot be born with CML. It happens because a piece of DNA in a bone marrow cell becomes damaged.

Certain risk factors increase an individual’s chances of developing CML. These include radiation exposure, age, and gender.

The risk of developing CML increases with age, and doctors diagnose most people between ages 60–65 years. CML represents just 2% of leukemias in children ages 15 or younger, or one case per million.

CML has three phases, and each stage has different symptom severity.

Chronic phase

In the chronic phase, fewer than 10% of the bone marrow and blood cells are leukemia cells. Most people in this phase do not have any symptoms.

Accelerated phase

In the accelerated phase, 10–19% of the bone marrow and blood cells are leukemia cells. As a result, most people experience symptoms such as feeling very tired, weight loss, night sweats, fever, and fullness or pain below the ribs on the left side.

Blastic phase

In the blastic phase, 20% or more of the bone marrow and blood cells are leukemia cells. If someone has symptoms of fever, tiredness, and an enlarged spleen, this is called a blast crisis. Doctors find this phase challenging to treat.

In addition to a physical exam and medical history, doctors use the following tests to diagnose CML:

  • Complete blood count: Someone with CML has an increased white blood cell count, a decreased red blood cell count, and a possible increase or decrease in platelet count.
  • Peripheral blood smear: A visual examination of blood cells where technicians can determine the number, size, shape, and type of blood cells, the specific pattern of white blood cells, and the proportion of immature to mature cells.
  • Bone marrow aspiration and biopsy: An examination of bone marrow cells to find abnormalities.
  • Cytogenetic analysis: An examination of chromosomes and chromosomal abnormalities. The Philadelphia chromosome, in particular, may confirm CML.
  • Quantitative polymerase chain reaction: The most sensitive test that measures the number of genes in bone marrow or blood samples.
  • Fluorescence in situ hybridization: A sensitive test that involves examining chromosomes in cells and genes.

Treatment success varies between the three phases of CML. Standard treatment is often helpful during the chronic phase but is not as effective during the accelerated phase. In addition, the blastic stage is challenging to treat.

Since most cases of CML occur in adults, the treatment of children with CML is not standardized. In most cases, treatment of CML in children follows the guidelines for adult CML treatment.

Targeted therapy

Targeted therapy uses drugs or other substances to find and attack the cancer cells. This treatment often causes less harm to noncancerous cells than chemotherapy and radiation therapy.


Immunotherapy uses the body’s own immune system to fight cancer cells. Manufactured substances help to boost, direct, or restore the body’s natural defenses.


Chemotherapy is a treatment that uses drugs to kill any fast-dividing cells. Since cancer cells grow and divide quickly, chemotherapy can effectively combat them.

Donor lymphocyte infusion

Donor lymphocyte infusion is a treatment option that may follow a stem cell transplant. Doctors remove lymphocyte white blood cells from the donor’s blood and infuse them into the person with CML. The lymphocytes recognize the cancer cells as not being part of the body and begin to attack them and reduce their numbers.

High-dose chemotherapy with stem cell transplant

Although high doses of chemotherapy kill cancer cells, they may also kill healthy blood-forming cells. Stem cell transplants replace the destroyed blood-forming cells and allow the person to produce normal blood cells.


If leukemia spreads to the spleen, the spleen can become swollen and cause issues with surrounding organs, causing symptoms. A surgery called a splenectomy is an option to remove the spleen. This helps with symptoms of an enlarged spleen and may improve blood cell and platelet counts in some people.

Most individuals with CML have a change in their genes called the Philadelphia chromosome.

In CML, some of the DNA from one chromosome transfers to another chromosome, and when it combines with the DNA there, it creates a new gene that causes the bone marrow to make an abnormal protein.

The Philadelphia chromosome is not genetic, and the cause of this mutation is unknown.

Chronic leukemias may take a long time until they cause any problems, but they are also harder to cure than other leukemias. In addition, the individual’s age, CML phase, number of blasts in the bone marrow or blood, and general health affect the treatment effectiveness and ultimate outlook.

CML can return after treatment, and when it relapses, the number of blast cells increases. CML is controllable in most people, but usually, no treatment completely cures the condition.

It is normal for people affected by cancer to feel anxious, depressed, or worried. Many people find it beneficial to seek help and support from family, friends, support groups, religious groups, or professional counselors.

Cancer Care offers free, professional support and resources for individuals affected by leukemia. People can also find personal support and information from the Leukemia and Lymphoma Society.

CML is a type of cancer affecting the myeloid cells. CML has chronic, accelerated, and blastic stages that depend on the level of leukemia cells in the bone marrow.

Doctors use various tests to diagnose CML, including a complete blood count, blood smear, and bone marrow biopsy. Treatment options for CML include targeted therapy, immunotherapy, chemotherapy, donor lymphocyte infusion, high-dose chemotherapy with stem cell transplant, and surgery.

Rather than curing CML, doctors usually control the condition with targeted therapy drugs.