Chronic Myeloid Leukemia
Chronic myeloid leukemia (CML) is one of the four basic types of leukemia. It tends to affect the adults and it is uncommon in children. The disease is based on immature blood cells. To be more precise, it develops from white blood cells belonging among the group of granulocytes.
In this case we know the mutation that causes the malignant transformation of the blood cell. It is a defect when chromosome 9 and chromosome 22 replace each other parts. This gives rise to abnormal gene sequence and that results in an uncontrollable multiplication of affected cell. Malignant white blood cell is no longer responsive to the control processes of the organism. Clones of the cell have the same properties and spread throughout the body.
Tumor cells settle in the bone marrow, lymph nodes and organs of the body. The tumor causes overproduction of immature white blood cells that can not properly fulfill the function of immune defense. In addition, it suppresses proper formation of other blood cells (healthy white blood cells, red blood cells) and platelets. The symptoms are initially nonspecific (fatigue, fever, night sweats, joint pain, etc), later there may occur symptoms of affection of tissues and organs with malignant cell clones (enlarged lymph nodes, enlarged spleen, etc).
The lack of red blood cells manifests as anemia with anemic syndrome. Deficiency of functional white blood cells leads to immunodeficiency and recurring infections. The lack of platelets causes increased risk of bleeding (bruising, frequent nosebleeds, blood in stool, blood in urine, etc).
Classic chronic myeloid leukemia has several stages. In the beginning there is a chronic phase lasting for several years when the symptoms are less visible or completely missing. Then there is the accelerated phase, which lasts for about a year. During this period the proliferation of tumor cells accelerates and the above mentioned symptoms worsen. The final stage is the so-called blastic crisis lasting only few months. Without proper treatment this last stage is fatal.
In medical history we should focus on the above mentioned symptoms. The outcome of the physical examination may be poor with the exception of discovering the spleen enlargement.
Blood count is important but more examinations need to be done to determine the right diagnosis. Hematologists can examine the white blood cells and confirm that they are clones of one tumor cell. It is important to obtain a sample of bone marrow cells (by sternal puncture) or a sample of bone marrow tissue (trephine biopsy, usually from the iliac crest). Special cytogenetic methods are used to prove presence of certain chromosomal alteration (the Philadelphia chromosome) inside the tumor cells that are typical for CML.
In the past, chemotherapy used to be the treatment of choice. With understanding the patophysiological mechanism of CML, the modern medicine proposes another option – the biological therapy. In this case it consist of administration of tyrosin kinases inhibitors. These drugs inhibit cell receptors known as tyrosine kinases, which are responsible for malignant behavior of the tumor cells. The most commonly used substance is so-called Imatinib. The effect of the treatment is usually satisfactory, but some people need a continuous use of the drug (otherwise the disease returns) and some forms of CML may eventually become totally resistant to the biological treatment. When there is no other option, bone marrow transplant may be performed.