Chronic Myelogenous Leukemia

Leukemia is cancer of the white blood cells. White blood cells form in the bone marrow and help your body fight infection. In leukemia, the bone marrow produces abnormal white blood cells. These cells crowd out the healthy blood cells, making it hard for blood to do its work. In chronic myeloid leukemia (CML), there are too many granulocytes, a type of white blood cell.

CML can also be called chronic myeloid leukemia and chronic granulocytic leukemia. CML typically affects older adults and rarely occurs in children, though it can occur at any age.

Sometimes CML does not cause any symptoms. If you have symptoms, they may include:

• Fatigue
• Weight loss
• Night sweats
• Fever
• Pain or a feeling of fullness below the ribs on the left side

Treatments for CML include chemotherapy, stem cell transplants, infusion of donated white blood cells following stem cell transplants, surgery to remove the spleen, and biologic and targeted therapies. Biologic therapy boosts the body's own ability to fight cancer. Targeted therapy uses substances that attack cancer cells without harming normal cells.

CML occurs when something goes wrong in the genes of your blood cells. It is not clear what initially starts this process, but doctors have discovered how it progresses into CML.

First, an abnormal chromosome develops. Human cells normally contain 23 pairs of chromosomes. These chromosomes hold the DNA that contains the instructions (genes) that control the cells in your body. In people with chronic myelogenous leukemia, the chromosomes in the blood cells swap sections with each other. A section of chromosome 9 switches places with a section of chromosome 22, creating an extra-short chromosome 22 and an extra-long chromosome 9. The extra-short chromosome 22 is called the Philadelphia chromosome, named for the city where it was discovered. The Philadelphia chromosome is present in the blood cells of 90 percent of people with CML.

Second, the abnormal chromosome creates a new gene. The Philadelphia chromosome creates a new gene. Genes from chromosome 9 combine with genes from chromosome 22 to create a new gene called BCR-ABL. The BCR-ABL gene contains instructions that tell the abnormal blood cell to produce too much of a certain protein that promotes cancer by allowing certain blood cells to grow out of control.

Third, the new gene allows too many diseased blood cells. Your blood cells originate in the bone marrow, a spongy material inside your bones. When your bone marrow functions normally, it produces immature cells (blood stem cells) in a controlled way. These cells then mature and specialize into the various types of blood cells that circulate in your body — red cells, white cells and platelets. In CML, this process does not work properly. The protein caused by the BCR-ABL gene causes too many white blood cells and most or all of these contain the abnormal Philadelphia chromosome. The diseased white blood cells do not grow and die like normal cells. The diseased white blood cells build up in huge numbers, crowding out healthy blood cells and damaging the bone marrow.

Factors that increase the risk of CML include:

• Older age
• Being male
• Radiation exposure, such as radiation therapy for certain types of cancer

Family history is not a risk factor for CML.

See your doctor for persistent fatigue, fever, night sweats, easy bleeding or bruising, unexplained weight loss, or fullness below the left ribs. Blood tests can diagnose CML, and treatment is most effective when started early.