blood disorders
Chronic Myeloid Leukemia (CML)
Introduction
Chronic myeloid leukemia is a slowly progressing disease in which cells that normally would develop into the types of White Blood Cells called neutrophils, basophils, eosinophils, and monocytes become cancerous and replace normal cells in the bone marrow. (See also Overview of Leukemia .) People pass through a phase in which they have nonspecific symptoms such as tiredness, loss of appetite, and weight loss. As the disease progresses, the lymph nodes and spleen enlarge, and people may also be pale and bruise or bleed easily. Blood tests, molecular testing, and chromosome analysis are used for diagnosis. Treatment is with drugs called tyrosine kinase inhibitors and is started even if the person has no symptoms. Sometimes, stem cell transplantation is necessary. Chronic myeloid leukemia (CML) may affect people of any age and of either sex but is uncommon in children younger than 10 years. The disease most commonly develops in adults between the ages of 40 and 60. The cause usually is a rearrangement of two particular chromosomes (9 and 22) into what is called the Philadelphia chromosome. The Philadelphia chromosome produces an abnormal enzyme (tyrosine kinase), which is responsible for the abnormal growth pattern increased production of the white blood cells in CML. Additional gene abnormalities (called mutations) that make CML more resistant to treatment sometimes occur. CML has three phases Chronic phase: An initial period that may last 5 to 6 years during which the disease progresses very slowly Accelerated phase: The disease begins to progress more quickly, treatments are less effective, and symptoms worsen Blast phase: Immature leukemia cells (blasts) appear and the disease becomes much worse, with complications such as serious infections and excessive bleeding In CML, most of the leukemia cells are produced in the bone marrow, but some are produced in the spleen and liver. In contrast to the acute leukemias, in which large numbers of blasts are present, the chronic stage of CML is characterized by marked increases in the numbers of normal-appearing white blood cells and sometimes platelets. During the course of the disease, more and more leukemia cells fill the bone marrow and others enter the bloodstream. When the leukemia cells crowd out normal blood-producing cells in the bone marrow, there is decreased production of one or more of the following: Red Blood Cells , which carry oxygen in the bloodstream White Blood Cells , which help defend the body against infection Platelets , small cell-like particles that help in the clotting process Cancerous white blood cells do not function like normal white blood cells so the cells of CML do not help defend the body against infection. The smaller number of healthy white blood cells makes infection more likely. Eventually the leukemia cells undergo more changes, and the disease progresses to an accelerated phase and then inevitably to the blast phase. In the blast phase, only immature leukemia cells are produced, a sign that the disease has become much worse. 