The majority of blood cells are formed in the bone marrow, a sponge-like tissue located in the large bones of the body. Normally, only as many new cells are formed as need to be replaced. The blood cells are formed from the so-called stem cells in the bone marrow. These divide and develop into myeloid and lymphatic cells. The blood cells ultimately differentiate from these precursor cells via various intermediate stages.
In AML, a precursor of the myeloid cell degenerates, divides uncontrollably and multiplies. The resulting non-functional blood cells are also known as myeloid blasts. The degeneration of the myeloid cell is based on a genetic change in the bone marrow. There are various risk factors for this:
- ionizing radiation
- genetic diseases such as trisomy 21
- increased contact with chemical substances such as benzene
- Cytostatic drugs (substances that inhibit cell growth)
The symptoms of acute myeloid leukemia usually develop rapidly within a few weeks. The excessive production of immature myeloid blasts leads to a lack of healthy blood cells. On the other hand, the leukemic cells also affect internal organs, causing various symptoms.
The lack of red blood cells, the so-called erythrocytes, is also known as anemia. Typical symptoms of such a blood deficiency are paleness, tiredness and fatigue. The reduction in white blood cells (leukocytes), which are an important part of the immune system, leads to fever and/or an increased susceptibility to infections of all kinds. Blood platelets, which play a decisive role in blood clotting, are also missing. This results in bruising, small punctiform bleeding spots (petechiae), frequent nosebleeds and prolonged bleeding times after minor injuries.
If the spleen or liver are affected by the immature blasts, they can swell. This is also referred to as (hepato)splenomegaly. The lymph nodes, for example in the neck, groin or armpits, may also swell. The spread of leukemia cells to the bones can lead to bone pain.
In rare cases, leukemia also affects the spinal cord or the meninges. Neurological symptoms such as nerve paralysis, headaches or visual disturbances can then occur. Deposits of blasts in the skin also occur rather rarely and sometimes lead to very conspicuous skin symptoms. Some patients, on the other hand, hardly show any symptoms, meaning that leukemia tends to be diagnosed by chance as part of a routine examination.
In many cases, leukemia is discovered by chance when patients consult a doctor due to the rather unspecific symptoms. The suspicion of acute myeloid leukemia is then confirmed during the physical examination if the spleen and liver or lymph nodes are enlarged. The blood usually shows anemia with a lack of red blood cells.
White blood cells and platelets may also be deficient. In acute leukemia, the so-called erythrocyte sedimentation rate, or ESR for short, is also significantly increased. The characteristic myeloid blasts can also be seen under the microscope. Despite these fairly clear findings, an examination of the bone marrow is required to make an exact diagnosis.
To do this, the doctor takes a sample of the bone marrow from the iliac crest under local anesthesia. Microscopic examination of this biopsy reveals a large number of blasts and at the same time a reduction in normal cells. Imaging procedures such as ultrasound (sonography) or X-rays as well as computer and magnetic resonance imaging make it clear whether the immature cell precursors have already affected internal organs. Infection of the meninges and spinal cord, on the other hand, can only be diagnosed by examining the cerebrospinal fluid.
The treatment of choice for acute myeloid leukemia is
intensified chemotherapy, which is administered in several phases. In the so-called
induction phase, patients receive high doses of chemotherapeutic agents such as cytosine arabinoside. This is intended to reduce the number of malignant cells. In the
consolidation phase, the dose of therapeutic agents is reduced. This second phase of chemotherapy lasts several months. In the subsequent
maintenance therapy, patients must continue to take the chemotherapeutic agents in low doses for a period of up to two years. An
allogeneic stem cell transplant can also be carried out. This involves transferring blood stem cells from a healthy donor to a sick recipient. Stem cell transplantation is carried out as part of the consolidation phase for patients at high risk.
The prognosis of acute myeloid leukemia depends on various factors. For example, the molecular profile, which takes into account the patient's age and any concomitant diseases, determines the likelihood of a relapse. The highest risk of relapse is within the first two to three years after the first occurrence of leukemia. For this reason, regular follow-up checks are necessary even after successful therapy, which include a physical examination as well as blood and bone marrow tests.
Overall, the chances of a cure for AML have improved in recent decades. However, as it is not possible to completely destroy the leukemic cells in all patients, the 5-year survival rate is only around 30 percent. This means that 30 percent of all patients with acute myeloid leukemia are still alive five years after diagnosis.
