What is myeloma?
Myeloma is a type of blood cancer that develops from plasma cells in the bone marrow. As bone marrow is found in multiple areas of the body, the disease is often called multiple myeloma.
Topics on this page:
- The blood
- Blood cell production and myeloma
- How myeloma affects the body
- Who gets myeloma?
- What causes myeloma?
The blood is pumped around your body to provide oxygen and nutrients to your tissues, and to remove waste products. It is made up of three main types of blood cells, and these have specific functions:
- Red blood cells – carry oxygen around the body
- White blood cells – fight infection
- Platelets – help the blood clot
All three types of blood cells live for a limited time and need to be continually replaced. Most are made in the bone marrow, which is the spongy part in the centre of the bones.
The bone marrow contains stem cells. These are unspecialised blood cells that develop into mature red or white blood cells or platelets. Once mature, the blood cells are usually released into the bloodstream to carry out their set functions.
A plasma cell is a special type of white blood cell. Like other white blood cells, plasma cells develop in the bone marrow and form part of the immune system that protects the body from infection.
The role of a plasma cell is to make proteins called antibodies or immunoglobulins. Once released into the blood, these antibodies attack and kill bacteria and viruses that have infected the body.
Blood cell production and myeloma
Stem cells turn into red or white blood cells or platelets. Plasma cells are one type of white blood cell.
Normally plasma cells produce antibodies that are released into the blood to fight infection. Myeloma cells are abnormal plasma cells. They release an abnormal antibody called paraprotein.
How myeloma affects the body
Myeloma begins when abnormal plasma cells (myeloma cells) start multiplying rapidly. Normal plasma cells make a wide variety of antibodies that help the body fight infections, but myeloma cells make an abnormal antibody known as paraprotein, M-protein or monoclonal protein. Paraprotein is found in the blood of most people who have myeloma.
Without treatment, myeloma can affect your health in various ways:
- Because the myeloma cells crowd out the bone marrow, there is limited space for normal blood cells to develop.
- The lack of normal plasma cells and other white blood cells can make a person more prone to infections.
- A lack of red blood cells (anaemia) can cause fatigue.
- A lack of platelets (thrombocytopenia) can cause bleeding and bruising.
- Because myeloma starts in the bone marrow, it can spread to the bones, making them weak and thin (osteoporosis).
- As bones start to break down, they may release too much calcium into the blood (hypercalcaemia), which can lead to nausea, confusion and kidney damage.
- The paraprotein released into the blood by the myeloma cells can cause problems in the kidneys, and damage the nerves in the hands and feet (peripheral nerves).
See Controlling symptoms for how these issues can be managed.
Cancerous plasma cells sometimes form a single tumour in the bone or tissue, rather than spreading throughout the bone marrow. Known as solitary plasmacytomas, these tumours are not common and make up only about 5% of plasma cell cancers.
Who gets myeloma?
Myeloma is not a common disease. About 1500 people in Australia are diagnosed with the disease each year. It accounts for 15% of blood cancers and 1% of all cancers generally.
Myeloma is rare in people under 40. The disease is being found more often in people over 60, which is partly explained by the ageing population. It is slightly more common in men than in women.
What causes myeloma?
The causes of myeloma are unknown. We know that plasma cells become cancerous when there are certain changes in their DNA (the chemical instructions for the actions of the cells). However, we do not yet know what triggers those DNA changes.
Exposure to certain chemicals (e.g. dioxins used in industry), high levels of radiation (e.g. from working in a nuclear power plant) and viruses (such as HIV) have been linked to an increased risk of myeloma and related diseases, but they have not been proven to cause it.
Myeloma is not considered to be hereditary (inherited) and there is little risk of passing it on to your children. It is rare for more than one person in a family to be affected by myeloma, although this does happen occasionally.