What is Chronic Myelogenous Leukemia?

Chronic myelogenous leukemia or CML is a very rare type of cancer, which starts in the bone marrow and slowly progresses to other parts of the body. Also known as chronic myeloid leukemia and chronic granulocytic leukemia, the disease typically affects older adults and causes an increase in the number of white blood cells in the body. Usually, people with CML do not develop any kind of symptoms of the condition until later stages, and it is mostly diagnosed during a routine blood test. Yet again, some patients might exhibit symptoms like bone pain, fever, weight loss, tiredness, loss of appetite, pain below the ribs, excessive sweating especially during nighttime, etc. Chronic myelogenous leukemia can make the patient prone to bleeding as well.

Causes of Chronic Myelogenous Leukemia

The condition is believed to happen because of a chromosome mutation in the bone marrow that occurs spontaneously. There is not much research to conclude what actually causes the genes to go awry, and it can vary from person to person. However, experts say that the development of the Philadelphia chromosome is the root cause in most of the chronic myelogenous leukemia cases.

The human body normally has 23 pairs of chromosomes, which contain the DNA that controls the cells in the body. In CML patients, the chromosomes in their blood cells switch sections with one another. To be precise, a section of chromosome 9 swaps its place with a section of chromosome 22, which creates an abnormal chromosome 22 as well as an elongated chromosome 9. This abnormal and very short chromosome 22 is known as the Philadelphia chromosome, which creates a new gene in the patient’s body. This gene combines with the one produced by the elongated chromosome 9, creating a mutated gene known as BCR-ABL. The BCR-ABL gene instructs the blood cells to produce excessive amounts of a protein known as tyrosine kinase, which in turn paves way for the growth of cancerous cells in the body.

Normally, when the blood cells are made in the bone marrow, they mature in a controlled way and then specialize in different types of blood cells to be circulated throughout the body. However, this does not happen as it should in the case of chronic myelogenous leukemia. The tyrosine kinase protein makes too much of white blood cells to grow instead of letting the blood cells mature into various types as needed in the body. Moreover, most of the white blood cells contain the mutated Philadelphia chromosome as well, and they do not grow or die like normal cells but accumulate inside the bone marrow. Eventually, the abnormal blood cells start to replace healthy blood cells and damage the bone marrow.

Phases of Chronic Myelogenous Leukemia

Chronic myelogenous leukemia is typically diagnosed during routine blood tests. To confirm the condition, doctors at community healthcare centers usually recommend bone marrow biopsy and bone marrow aspiration, wherein bone marrow samples are collected from the hipbone of the patient and sent for laboratory testing. Moreover, blood chemistry tests are also done to check the organ functions of the patient. In some cases, specialized tests to check for the growth of the Philadelphia chromosome, such as polymerase chain reaction (PCR) test and fluorescence in situ hybridization (FISH) analysis, are also recommended. The results of the diagnostic tests help the doctor to understand how severe the condition is.  

There are three stages of chronic myelogenous leukemia: chronic, accelerated, and blast. Generally, healthcare experts figure out the phase of the disease by checking the percentage of abnormal blood cells in the bone marrow. In the chronic phase, the condition would have just started to affect the body, which means that the patient is more likely to recover fully following the treatment. In the accelerated phase, the disease would have grown to a more severe condition and might require specialized treatment like bone marrow transplant. The blast phase is the most severe stage, which can be life-threatening if not dealt with proper care.

Treatment Options for Chronic Myelogenous Leukemia

Targeted drug therapy is the most common treatment option recommended for chronic myelogenous leukemia patients. Here, the target of the drugs is to block the production of the tyrosine kinase protein. The common targeted drugs for CML include bosutinib, imatinib, ponatinib, nilotinib, and dasatinib. However, some of these medications can cause side effects like swelling of the skin, diarrhea, nausea, fatigue, skin rashes, and muscle cramps. In severe cases, doctors might also prescribe other targeted drugs, such as omacetaxine, to block the action of the abnormal BCR-ABL gene.

Bone marrow transplant or stem cell transplant is recommended to more advanced cases of chronic myelogenous leukemia. This is because the procedure entails some serious risks and can lead to other complications as well. Chemotherapy might also be recommended in severe cases if targeted drug therapy failed to help the patient. However, this treatment could also have some serious side effects depending upon the chemotherapy drug administered to the patient.