Understanding Chronic Myeloid Leukemia
Chronic myeloid leukemia (CML) is a slow-growing type of leukemia Leukemia: an acute (progresses quickly) or chronic (takes a longer time to progress) disease of the blood and bone marrow; characterized by an abnormal increase in blood cells in which the body makes an uncontrolled number of abnormal blood cells.
Causes of Chronic Myeloid Leukemia
Understanding what causes CML starts with understanding the role of chromosomes Chromosome: a part of a cell that contains genes, the basic units that carry hereditary information. An individual chromosome can contain hundreds or thousands of genes , structures in your cells that contain DNA and other genetic material. DNA within the chromosomes provides instructions for blood cells to be made in your bone marrow Bone marrow: the soft tissue inside bones that produces blood cells.
In CML, the body makes an uncontrolled number of abnormal blood cells. In almost all patients with CML:
- Inside a cell, pieces of 2 separate chromosomes break off and join together, forming an abnormal chromosome called the Philadelphia chromosome Philadelphia chromosome (or Ph chromosome):the chromosome abnormality that causes CML; pieces from 2 different chromosomes break off and fuse together to create this new abnormal chromosome (or Ph chromosome).
- The Philadelphia chromosome then makes an abnormal protein called BCR-ABL BCR-ABL: an abnormal protein that causes out-of-control production of CML cells .
- The BCR-ABL protein causes the uncontrolled production of CML cells in the blood.
When you have CML, the BCR-ABL protein causes the bone marrow to produce more white blood cells White blood cells: blood cells that help fight infections. When the level of a certain type of white blood cell is lower than normal, it is called neutropenia , even when they are not needed. These are mostly damaged or immature. Over time, these extra, unhealthy white blood cells overcrowd healthy white blood cells, red blood cells Red blood cells: blood cells that carry oxygen to all parts of the body. When red blood cell levels are lower than normal, it is called anemia , and platelets Platelets: cell fragments that help stop bleeding. When platelet levels are lower than normal, it is called thrombocytopenia . The immature white blood cells are called blast cells Blast cells: immature white blood cells found in abnormally large numbers in CML patients , or blasts.
Phases of Chronic Myeloid Leukemia
There are 3 phases of CML. They are defined by the percentage of blasts in the bone marrow, compared with other blood cells:
- Most patients are diagnosed in this phase; can last for months or years
- Less than 10% of blood cells in the bone marrow sample are blast cells
- In this phase of CML, leukemia Leukemia: an acute (progresses quickly) or chronic (takes a longer time to progress) diseases of the blood and bone marrow; characterized by an abnormal increase in blood cells cells grow more quickly
- 10%-19% of blood cells in the bone marrow sample are blast cells
- This is the most serious phase of CML; CML is more aggressive in this phase
- At least 20% or more blood cells in the bone marrow sample are blast cells