Chronic myelogenous leukemia is cancer of the bone marrow.

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

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

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, like thyroid cancer or Hodgkin's lymphoma. However, the vast majority of people treated for cancer with radiation do not go on to develop leukemia. It takes many years to develop leukemia from this cause.

Chronic myelogenous leukemia is grouped into several phases.

The chronic phase that can last for months or years. The disease may have few or no symptoms during this time. Most people are diagnosed by during this stage, when they are being tested for something else.

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

If untreated, CML progresses to the blast crisis phase. This phase is very difficult to treat and is marked by a very high count of immature white blood cells (leukemia cells). Bleeding and infection may occur due to bone marrow failure.

Other possible symptoms include:

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

A physical examination often reveals an enlarged spleen. A CBC shows an increased number of white blood cells.

Other tests that may be done include:

• CBC differential
• Bone marrow aspiration
• Testing for the presence of the Philadelphia chromosome
• Molecular assay for the bcr-abl gene

This disease may also alter the results of the following tests:

• Vitamin B-12 level
• Uric acid
• Platelet count