Multiple myeloma (MM) is an incurable blood cancer that starts in the bone marrow and is characterized by an excess amount of abnormal plasma cells. These are called myeloma cells and they produce high levels of abnormal antibody or M-proteins that are found in blood and urine, leading to impairment of normal marrow function and damaged bone.
A word about bone marrow
Bone marrow is the soft, sponge-like tissue in the centre of most bones. It consists mainly of two cell types: stromal cells, that maintain the bone marrow structure, and
stem cells.
Stem cells are undifferentiated cells, which means that they have not yet reached their final cell form and do not yet perform their definitive cell function. All our blood cells evolve from such stem cells:
- red blood cells, the carriers of oxygen
-
white blood cells, which form our immune system
- platelets, which have a function in blood clotting and healing wounds
The bone marrow’s most important role is to supply the blood with sufficient quantities of fresh blood cells.
About our immune system
The immune system is composed of different types of cells that work together in order to fight infections. Cells destined to become immune cells exist in the bone marrow and develop from stem cells.
Some stem cells develop into the small white blood cells called lymphocytes. The two major classes of lymphocytes are B cells (B lymphocytes) and T cells (T lymphocytes).
When B cells respond to an infection, they mature and change into plasma cells. Plasma cells live mainly in the bone marrow. The role of plasma cells is to produce and release proteins called antibodies or immunoglobulins to attack and help kill disease-causing germs such as bacteria and viruses.
A plasma cell is a fully differentiated cell. It has reached its final cell form and performs its specific task: the production of antibody proteins to fight infections. Plasma cells die when they are no longer needed. Every single plasma cell releases only one antibody and its make up is inherited by its descendents. This means that all copies (clones) of the same plasma cell can only release the same antibody as did their “ancestor”. That’s why this specific antibody protein is called a monoclonal protein or M protein.
Myeloma starts when a plasma cell becomes abnormal: the abnormal cell starts to divide in order to make copies of itself. These new cells divide repeatedly, making more and more abnormal cells. Abnormal plasma cells are called myeloma cells. Over time, as the cancer develops and plasma cells become detectable in the blood, and can spread to other ‘multiple’ sites in the body, hence the name multiple myeloma (MM). In short, MM develops when plasma cells in the bone marrow multiply instead of die.
When plasma cells grow out of control, they can produce a tumour. These tumours generally develop in the bone marrow, but it is not unusual for them to collect in the solid part of the bone or in other organs as well.
Some facts about Multiple Myeloma
- Multiple myeloma is the second most prevalent blood cancer after non-Hodgkin's lymphoma
- The average age of diagnosis is 60-65 years; however, the incidence of the disease in younger people is on the increase and the average age at diagnosis is decreasing. More than 2% of myeloma patients are under 40 years old at diagnosis.
- The incidence of Multiple Myeloma increases with age:
- <65 years: 1.5 to 2.5 in 100,000.
- >65 years: 25 to 30 in 100,000.
- Multiple myeloma affects slightly more men than women and there is a higher incidence in Afro-Caribbean ethnic groups compared to Caucasians
symptoms of multiple myeloma>>
Item code: NPR/09-0062
Date of Preparation: October 2009
