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General Information About Chronic Myelogenous Leukemia
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 bone marrow makes blood stem cells (immature cells) that develop into mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. The lymphoid stem cell develops into a white blood cell. The myeloid stem cell develops into one of three types of mature blood cells:
- Red blood cells that carry oxygen and other materials to all tissues of the body.
- Platelets that help prevent bleeding by causing blood clots to form.
- Granulocytes (white blood cells) that fight infection and disease
Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.
In CML, too many blood stem cells develop into a type of white blood cell called granulocytes. These granulocytes are abnormal and do not become healthy white blood cells. They may also be called leukemic cells. The leukemic cells can build up in the blood and bone marrow so there is less room for healthy white blood cells, red blood cells, and platelets. When this happens, infection, anemia, or easy bleeding may occur.
This summary is about chronic myelogenous leukemia. See 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. 
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.
WebMD Public Information from the National Cancer Institute
This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http://cancer.gov or call 1-800-4-CANCER
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