Introduction

Leukemia is cancer of the blood cells, usually the white blood cells. Chronic myeloid leukemia (CML) is most common in older adults. The average age of diagnosis is about 55 to 60 years old. Chronic myeloid leukemia is also known as CML, chronic myelogenous leukemia, chronic granulocytic leukemia, and chronic myelocytic leukemia. An estimated 4,870 new cases of CML were diagnosed in 2010, according to the American Cancer Society.

Bone marrow is the soft tissue inside bones where blood cells are made. CML occurs when the bone marrow makes too many unformed cells called blasts. Blasts normally become white blood cells that fight infection. But in CML, the blasts do not develop and cannot fight infection. Large numbers of these defective cells collect in bone marrow and blood.

CML is a “chronic” leukemia because the number of abnormal cells in the bone marrow increases gradually. These abnormal “leukemia cells” eventually crowd out the red blood cells, white blood cells, and platelets (blood cells that help make blood clot) that the body needs. CML can develop over a period of months or years.

People with CML usually have no symptoms at first. Eventually, they start feeling generally ill. They tire more easily and feel short of breath when they are physically active. Some patients become pale from the anemia (loss of red blood cells) caused by CML. Many patients feel discomfort on the left side of the abdomen from an enlarged spleen. Some patients sweat a great deal, lose weight, and cannot tolerate warm temperatures.

Patients with CML have a specific chromosome abnormality, called the Philadelphia chromosome abnormality (it was discovered by researchers in Philadelphia). Part of chromosome No. 9 breaks off and attaches itself to chromosome No. 22. This changes the position and functions of certain genes, which makes CML cells grow and spread. People with CML sometimes have other abnormal chromosomes.