Chronic myelogenous leukemia is cancer that starts inside bone marrow, the soft tissue inside bones that helps form blood cells. The cancer grows from cells that produce white blood cells.

See also:

• Acute myeloid leukemia (CML)
• Chronic lymphocytic leukemia (CLL)
• Leukemia

CML can occur in adults (usually middle-aged) and children. The disease affects 1 to 2 people per 100,000 and makes up 7 - 20% cases of leukemia. It is usually associated with a chromosome abnormality called the Philadelphia chromosome.

Exposure to ionizing radiation is one possible trigger for this chromosome abnormality. Such exposure could occur from a nuclear disaster or from treatment of a previous cancer such as thyroid cancer or Hodgkin's lymphoma. It takes many years to develop leukemia from this cause. However, most people treated for cancer with radiation do not go on to develop leukemia, and most patients with CML have not been exposed to radiation.

CML causes rapid growth of the blood-forming cells (myeloid precursors) in the bone marrow, blood, and body tissues.

Chronic myelogenous leukemia is grouped into several phases:

• Chronic
• Accelerated
• Blast crisis

The chronic phase can last for months or years. The disease may have few or no symptoms during this time. Most people are diagnosed during this stage, when they are having blood drawn for other reasons.

The accelerated phase is a more dangerous phase, during which the leukemia cells grow more quickly. This phase may be associated with fever (without infection), bone pain, and a swollen spleen.

If untreated, CML progresses to the blast crisis phase. Bleeding and infection may occur due to bone marrow failure. Other possible symptoms include:

• Bleeding and bruising
• Excessive sweating (night sweats)
• Fatigue
• Low-grade fever
• Pressure under the left ribs from a swollen spleen
• Sudden appearance of small red marks on the skin (petechiae)
• Weakness