Chronic myeloid leukemia (CML) is also commonly known as blood cancer. It is a chronic disease characterized by a marked increase in white blood cells (leukocytes) in the bone marrow and in the blood.
Further information and specialists in chronic myeloid leukemia can be found below.
Like polycythemia vera rubra and osteomyelosclerosis, CML is a myeloproliferative neoplasm—a disease of the bone marrow.
The incidence (prevalence) is two cases per 100,000 people per year. The disease most commonly affects people between the ages of 50 and 60.
The Causes of Chronic Myeloid Leukemia
CML is caused by a mutation in the multipotent hematopoietic progenitor cell. These blood stem cells are found primarily in the bone marrow.
They are responsible for the entire production of blood cells and the immune system. In CML, one of these stem cells becomes malignant and produces white blood cells—granulocytes—uncontrollably.
And they do so in very large quantities. Although these cells are functional, they displace the other cells in the bone marrow and, later, in the blood as well.
It is not yet clear exactly why stem cells become malignant. Triggering factors may include benzene, ionizing radiation (such as that emitted by radioactive substances), and chemotherapy drugs.
In addition, experts have detected the Philadelphia chromosome in about 90 percent of patients with chronic myeloid leukemia. A link between this chromosomal break in the region of chromosome 22 and the development of CML is therefore considered very likely.
The Symptoms and Stages of CML
Chronic myeloid leukemia can generally be divided into three stages:
- Chronic Phase
- Accelerated Phase
- Blast Crisis
The chronic phase begins gradually. Often, those affected do not realize they are ill for years. Enlargement of the spleen (splenomegaly) is frequently the first and only symptom of the chronic phase.
Since abnormal cells displace healthy blood cells from the bone marrow, the body produces blood in the liver and spleen. This leads to swelling of these organs, which can cause a feeling of pressure in the upper abdomen. However, CML is often diagnosed incidentally at this stage.
For example, a routine blood test may reveal an increase in white blood cells. Doctors refer to this as leukocytosis. Typically, the blood count reveals not only mature granulocytes (a type of white blood cell) but also immature precursors. At this stage, the proportion of immature cells (blasts) is still below ten percent.
The acceleration phase marks the transition from the chronic phase to the blast crisis. The number of white blood cells in the blood increases steadily. At the same time, there is a deficiency of red blood cells and platelets.
Anemia manifests itself through the following symptoms:
- Fatigue
- Susceptibility to infection
- Paleness
- Hair loss
- Headaches
- Shortness of breath on exertion
A deficiency of blood platelets (thrombocytes) leads to an increased tendency to bleed. Patients are more likely to experience nosebleeds or develop larger bruises from minor injuries.
Pinpoint skin hemorrhages (petechiae) and bruises (hematomas) are common @ Eberhard /AdobeStock
The acceleration phase is characterized by a marked increase in splenomegaly. In the blood count, the blast percentage now reaches up to 30 percent.
Patients feel significantly weakened, and their general well-being is poor. In most cases, the blast crisis occurs suddenly after the acceleration phase or immediately after the first phase.
The slow progression gives way to an acute phase of the disease. The proportion of immature cells in the blood exceeds 30 percent. Large numbers of CML cells are now also found outside the bone marrow. During the blast crisis, patients feel very unwell.
They suffer from:
- Increased susceptibility to infection
- Fatigue
- Exhaustion
If left untreated, this stage is fatal within a few days or weeks.
Treatment of Chronic Myeloid Leukemia
CML is currently not curable with medication.
The goal of drug therapy is to prevent the disease from progressing to the next stage and to improve patients’ quality of life. Doctors assess the success of treatment based on hematological, cytogenetic, and molecular remission.
Treatment success is determined by:
- The degree to which blood counts have normalized
- Reduction in spleen enlargement
- Other laboratory parameters from blood and bone marrow tests
Doctors monitor these regularly. Ideally, the blood count returns to normal within a few days of starting treatment.
In most cases, treatment begins with medications from the group of tyrosine kinase inhibitors. These are drugs that inhibit a specific enzyme activity and, consequently, the division of leukemia cells.
Well-known active ingredients in this group include:
- Imatinib
- Nilotinib
The administration of interferon-α is also part of the standard treatment for CML. IFN-α is a signaling molecule that prevents the division of leukemia cells. However, therapy with cytokines (cell growth-regulating proteins) often leads to side effects. These side effects can result in premature discontinuation of treatment.
In more severe forms of CML, white blood cell counts can also be normalized using the cytostatic drug hydroxycarbamide. Chemotherapeutic agents such as hydroxycarbamide are used when white blood cell counts are high or to prepare for a stem cell transplant.
Stem cell transplantation is the only treatment that offers the prospect of a cure for CML. The patient receives purified and filtered blood stem cells from a donor via infusion.
However, for the treatment to be effective, the patient first undergoes chemotherapy and radiation therapy to destroy the abnormal bone marrow cells.
Since this process kills not only diseased cells but also healthy ones, a stem cell transplant is no longer possible in more advanced stages of the disease.
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