Chronic myelogenous leukemia is a disease in which the bone marrow makes too many white blood cells.

Chronic myelogenous leukemia (also called CML or chronic granulocytic leukemia) is a slowly progressing blood and bone marrow disease that usually occurs during or after middle age, and rarely occurs in children. Normally, the body produces bone marrow stem cells (immature cells) that develop into mature blood cells.

There are 3 types of mature blood cells:

• Red blood cells that carry oxygen and other materials to all tissues of the body.
• White blood cells that fight infection and disease.
• Platelets that help prevent bleeding by causing blood clots to form.

In CML, the body tells too many bone marrow stem cells to develop into a type of white blood cell called granulocytes. Some of these bone marrow stem cells never become mature white blood cells. These are called blasts. Over time, the granulocytes and blasts crowd out the red blood cells and platelets in the bone marrow.

This summary is about chronic myelogenous leukemia. Refer to the following PDQ summaries for more information about leukemia:

• Adult Acute Lymphoblastic Leukemia Treatment
• Childhood Acute Lymphoblastic Leukemia Treatment
• Adult Acute Myeloid Leukemia Treatment
• Childhood Acute Myeloid Leukemia/Other Myeloid Malignancies Treatment
• Chronic Lymphocytic Leukemia Treatment
• Hairy Cell Leukemia Treatment

Possible signs of chronic myelogenous leukemia include tiredness, night sweats, and fever.

These and other symptoms may be caused by CML. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:

• Feeling very tired.
• Weight loss for no known reason.
• Night sweats.
• Fever.
• Pain or a feeling of fullness below the ribs on the left side.

Sometimes CML does not cause any symptoms at all.

Most people with CML have a gene mutation (change) called the Philadelphia chromosome.

Every cell in the body contains DNA (genetic material) that determines how the cell looks and acts. DNA is contained inside chromosomes. In CML, part of the DNA from one chromosome moves to another chromosome. This change is called the "Philadelphia chromosome." It results in the bone marrow making an enzyme, called tyrosine kinase, that causes too many stem cells to develop into white blood cells (granulocytes or blasts).

The Philadelphia chromosome is not passed from parent to child.

Tests that examine the blood and bone marrow are used to detect (find) and diagnose chronic myelogenous leukemia.

The following tests and procedures may be used:

• Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease such as an enlarged spleen. A history of the patient’s health habits and past illnesses and treatments will also be taken.
• Complete blood count (CBC): A procedure in which a sample of blood is drawn and checked for the following:
  • The number of red blood cells, white blood cells, and platelets.
  • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
  • The portion of the sample made up of red blood cells.
  
  
  Complete blood count (CBC). Blood is collected by inserting a needle into a vein and allowing the blood to flow into a tube. The blood sample is sent to the laboratory and the red blood cells, white blood cells, and platelets are counted. The CBC is used to test for, diagnose, and monitor many different conditions.
• Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that produces it.
• Cytogenetic analysis: A test in which cells in a sample of blood or bone marrow are viewed under a microscope to look for certain changes in the chromosomes, such as the Philadelphia chromosome.
  
  Philadelphia chromosome. A piece of chromosome 9 and a piece of chromosome 22 break off and trade places. The bcr-abl gene is formed on chromosome 22 where the piece of chromosome 9 attaches. The changed chromosome 22 is called the Philadelphia chromosome.
• Bone marrow aspiration and biopsy: The removal of bone marrow, blood, and a small piece of bone by inserting a needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for abnormal cells.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis (chance of recovery) and treatment options depend on the following:

• The patient’s age.
• The phase of CML.
• The amount of blasts in the blood or bone marrow.
• The size of the spleen at diagnosis.
• The patient’s general health.