What causes chronic myelogenous leukemia?
Chronic myelogenous leukemia is a rare type of leukemia that tends to affect older males. More than 90% of cases are due to a gene abnormality caused when two chromosomes swap sections with each other. There are 23 chromosomes in humans, and in patients with chronic myelogenous leukemia chromosomes 9 and 22 within blood cells exchange bits of genetic material to form a Philadelphia chromosome, named after the city where it was discovered. The new gene on this chromosome makes a protein called tyrosine kinase that allows white blood cells to grow out of control; moreover, these abnormal white blood cells tend not to become old and die. The bone marrow, where red blood cells, white blood cells, and platelets are made, becomes filled with white blood cells crowding out the normal cells and damaging the bone marrow itself. This can impair the ability of the bone marrow to manufacture normal amounts of blood cells.
What are the symptoms of chronic myelogenous leukemia?
Later symptoms of chronic myelogenous leukemia are due to decreasing function of the bone marrow and include:
- Bone and joint pain may occur as the bone marrow pressure increases due to
an excess build-up of white blood cells.
- Fatigue may be due to anemia because not enough red blood cells are being
produced and bleeding can occur if not enough platelets are being manufactured.
- In some patients with chronic myelogenous leukemia their
bone marrow makes too many platelets and they can develop abnormal blood
clotting, which can cause strokes.
- In chronic myelogenous leukemia there are too many white blood cells, but
these white blood cells tend not to function properly and their ability to fight
infection is compromised, which leads to an increased risk of infection.
- The increased numbers of white blood cells spill out of the bone marrow and start circulating in the blood stream and eventually become trapped in the spleen, causing it to enlarge.
How is chronic myelogenous leukemia diagnosed?
The diagnosis of chronic myelogenous leukemia is usually via a blood test called a complete blood count (CBC). Complete blood count is a common blood test that measures the number, type, and characteristics of red and white blood cells and platelets. Abnormal numbers of cells being produced are noted on the CBC and chronic myelogenous leukemia is diagnosed by reviewing a smear of the blood under a microscope. A bone marrow sample examines the area where the cells are made, and if the diagnosis of chronic myelogenous leukemia is being considered, this can be tested for the Philadelphia chromosome.
What is the treatment for chronic myelogenous leukemia?
Chronic myelogenous leukemia is a treatable disease with drugs that target the abnormal enzyme responsible for the faulty white blood cells. Imatinib (Gleevec), dasatinib (Sprycel), and nilotinib (Tasigna) shut down the tyrosine kinase enzyme and can keep chronic myelogenous leukemia in remission, but once the drug is started, the patient will likely need to take the medication throughout their lifetime. If the leukemia reactivates, a next option of treatment is a bone marrow transplant, which has a long-term cure rate of 60%-80%.
What is the outlook (prognosis) for chronic myelogenous leukemia?
The ability listen to your body is an important first step in finding a problem so it can be properly diagnosed and treated. Often, chronic myelogenous leukemia is diagnosed when a patient has a routine screening blood test. It's no different than finding a problem when taking your car in for an oil change; if a problem is found early the car can be fixed. However, if the problem is ignored, issues mount and the car engine cannot be repaired. People are no different. Ignoring warning signs and symptoms can make a treatable condition terminal.
REFERENCE: Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.