Leukemias-General
The word ' leukemia ' refers to a series of diseases that affect the blood system. So there are different kinds, but by ease, we will regularly use "leukemia ", in the singular.
Their starting point is in the bone marrow that makes the blood cells (white and red cells, platelets). In the case of leukemia, the production of white blood cells by the bone marrow is deeply disturbed. Large amounts of abnormal cells are produced and invade the bone marrow to then spread into the bloodstream and lymphatic system. They can also invade vital organs.
Anatomy of blood and bone marrow
Different types of cells
Blood contains different types of cells:
The composition of blood
Red blood cells (erythrocytes)
They provide oxygen transport from the lungs to the various tissues and organs.
White blood cells (leukocytes)
They are responsible for detecting and eliminating pathogens, such as bacteria and viruses that have penetrated the organism. They protect us against different forms of infections. At the same time, they eliminate dead and damaged cells, thus contributing to wound healing. Leukocytes are divided into three "groups" of cells: granulocytes, lymphocytes, and monocytes.
Blood platelets (thrombocytes)
They intervene in the coagulation of the blood, so that, following a rupture of a blood vessel (injury, internal bleeding), the loss of blood remains limited.
Each of these blood cells is of paramount importance.
Bone marrow
The formation of the blood cells takes place mainly at the level of the bone marrow. It is a spongy tissue that is inside the bones in the medullary cavity (the bone area occupied by the marrow). This is where the stem cells that form the different blood cells are housed. After a maturation process, these blood cells are released into the bloodstream.
There are two types of bone marrow:
Active bone marrow
It is red in colour and produces blood cells (white cells, red blood cells, platelets).
Bone marrow "Reserve "
Yellow, it is rich in fat cells.
In children, the skeleton provides less space for bone marrow than it does in adulthood. All the available medullary space is therefore occupied by bone marrow which produces blood cells in an extremely intense way.
In adults, all available medullary space is not necessary for the formation of blood cells. The active bone marrow is mainly located in the pelvis, vertebrae, ribs, sternum, and skull.
Some figures
All types, more than 1,600 new cases of leukemia are recorded each year in Belgium. In 2011, the Cancer registry identified 1,645 new cases of leukemia: 696 in women and 949 in men.
The average age of patients varies depending on the type of leukemia:
Acute lymphocytic leukemia: mainly in children and young adults
Acute myeloid leukemia: mainly in adults and rarely in children chronic lymphocytic leukemia: especially in the elderly
Chronic myeloid leukemia: especially in middle-aged patients (this also applies to myelodysplastic syndrome)
Although this is a relatively rare condition, leukemia is the most common form of childhood cancer.
Classification of Leukemias
Leukemia is defined by two characteristics: the speed of its progression (acute or chronic) and the type of abnormal white blood cells involved (lymphoid or myeloid). So there are several types of leukemia.
Acute or chronic Progression
To distinguish between acute and chronic leukemia, a classification was established according to the degree of maturity of abnormal cells (leukemic):
Acute leukemia
Abnormal cells fail to mature.
Consequence: A rapid accumulation of immature white blood cells.
Symptoms appear in a few weeks.
Chronic leukemia
Abnormal cells reach a relative degree of maturity.
Consequence: The process takes place more slowly.
Symptoms appear later.
This distinction is based on examinations of bone marrow and blood. It is important to determine the treatment. The course of the disease can also vary for each of these different forms.
Myeloid or lymphoid cells
The classification also takes into account the particular type of abnormal blood cells involved. Leukemia can therefore be of a nature:
Myeloid: In case of abnormal myeloid cells
Lymphoid: In case of abnormal lymphoid cells
4 Types of leukemia
Depending on the type of cell and the speed at which the disease evolves, 4 main types of leukemias are distinguished:
Acute lymphocytic leukemia
Acute myeloid leukemia
Chronic lymphocytic leukemia
Chronic myeloid leukemia
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