What is myeloma?
Myeloma is a cancer of the plasma cells. Plasma cells are mature lymphocytes (a type of white blood cell) that help fight infection by producing special proteins known as antibodies or immunoglobulins. Immunogblobulins (Ig) are produced by plasma cells in response to bacteria, viruses and other harmful substances found in the body.
Myeloma develops when plasma cells undergo a cancerous or malignant change and become myeloma cells. These myeloma cells multiply without any proper order and form collections known as tumours that accumulate in different parts of the body, especially in the bone marrow and on the surfaces of different bones in the body. These tumours secrete chemicals that stimulate other bone marrow cells (osteoclasts) to remove calcium from the bone. As a result bones can become weaker, more brittle and break more easily.
As myeloma cells multiply, they crowd the bone marrow and prevent it from making normal numbers of red cells (causing anaemia), white cells (increasing your susceptibility to infections) and platelets (increasing your susceptibility to bleeding and bruising). Myeloma cells can also interfere with the production of normal antibodies. Myeloma cells produce an abnormal type of immunoglobulin called paraprotein (also known as monoclonal immunoglobulin, myeloma protein, or simply M protein). Sometimes an excessive number of fragments of immunoglobulin known as light chains are produced. These light chains can be detected in the blood and they also appear in the urine. Light chains detected in the urine are called Bence-Jones protein.
What are the stages and types of myeloma?
Knowing the exact stage of your disease is important because it provides more information about the likely course of your disease (prognosis) and the best way to treat it. Myeloma can be classified according to how the disease is distributed in your body. The International Staging System (ISS) is based on two tests and defines three stages of myeloma:
- Stage I is early disease
- Stage II is in between Stage I and Stage III
- Stage III is advanced disease, where there is a large amount of myeloma in the body.
The CRAB criteria is often used to identify whether a person has active myeloma, which may require treatment. The acronym CRAB consists of: (C) increased calcium level (R) renal (kidney) problems (A) anaemia and (B) bone changes (lytic lesions or bone loss). One or more of these CRAB symptoms indicates symptomatic myeloma, which requires treatment. In the majority of cases myeloma is found in multiple bone marrow sites at diagnosis, which is why the disease is often called multiple myeloma. Sometimes an isolated collection of myeloma cells is found in only one site. When this happens the disease is described as a solitary myeloma or solitary plasmacytoma. Plasmacytomas can sometimes be successfully treated using radiotherapy alone.
Myeloma can also be classified according to the type of immunoglobulin (Ig) being secreted by the myeloma cells, and how it affects the body. Types of myeloma include:
- IgG myeloma - this is the most common type of myeloma, representing 50–60% of all cases
- IgA myeloma - represents about 20% of all cases
- Bence Jones myeloma or light chain myeloma - where the immunoglobulin’s light chains only are excreted in the urine, represents about 20% of cases
- IgM, IgD, IgE and non-sectretory myeloma - are all very rare types of myeloma.
Some people have an increased number of plasma cells in their bone marrow, but do not fit the criteria for a diagnosis of multiple myeloma. Their disease may be classified as ‘MGUS’ or smouldering myeloma:
- Monoclonal gammopathy of undetermined significance (MGUS) - is a non-malignant (non-cancerous) condition related to myeloma. It also involves the production of paraprotein by plasma cells. MGUS does not cause any symptoms and it is usually picked up during a routine blood or urine test. People diagnosed with MGUS do not require any treatment apart from regular follow-up by their doctor, usually on a yearly basis to have their protein levels checked. Over time a small number of people with MGUS will develop myeloma.
- Smouldering myeloma - is a very early phase of myeloma with no symptoms, but a bone marrow biopsy shows definite evidence of myeloma. People diagnosed with smouldering myeloma do not need treatment straight away. Treatment is given at a later stage, when the disease progresses after some months or years.
How common is myeloma?
Myeloma is a relatively rare disease. It accounts for approximately 1% of all cancers and 10% of all blood and bone marrow cancers. Each year in Australia around 1,500 people are diagnosed with myeloma.
Who gets myeloma?
Myeloma mainly affects older people, with an average age of 70 years at the time of diagnosis. Rarely, myeloma can affect people in their 20s and 30s. Myeloma is more common in men than women.
What causes myeloma?
The cause of myeloma remains mainly unknown. You cannot ‘catch’ myeloma by being in contact with someone who has it. There are rare cases where myeloma occurs in families, though in the vast majority of cases people who are diagnosed with myeloma have no family history of the disease. There are certain factors that may put some people at a higher risk of developing myeloma. These include exposure to high doses of radiation and ongoing exposure to certain industrial or environmental chemicals. Some people with MGUS will eventually go on to develop myeloma.
What are the symptoms of myeloma?
The symptoms of myeloma depend on how advanced the disease is. In the earliest stages, there may be no symptoms and myeloma is picked up during a routine blood test. The most common symptom of myeloma is bone pain. This is usually felt in the back or ribs and may be made worse by movement. Bone pain is usually the result of the gradual erosion of bone caused by substances secreted by myeloma cells. Over time bones can become weakened and thinned (osteoporosis) and holes (lytic lesions) may develop, increasing the risk of fracture (the bone breaking). When bone tissue is damaged, calcium is released from the bone into the bloodstream. An excess of calcium in the blood is called hypercalcaemia. If you have a higher than normal calcium level in your blood you may feel nauseated, constipated, tired, thirsty or even confused.
There are many causes of kidney damage in myeloma. The paraprotein produced by the myeloma cells can damage the kidneys. This is especially the case when the Bence Jones protein is involved. Other factors such as dehydration and hypercalcaemia can also cause kidney damage. The symptoms of this may include fatigue, mental confusion, swollen ankles and altered urinary output. Other symptoms of myeloma arise when these cancer cells crowd the bone marrow and prevent it from making normal blood cells and may include:
- anaemia due to a lack of red cells and causing persistent tiredness, dizziness, paleness, or shortness of breath when physically active
- frequent or repeated infections and slow healing due to a lack of normal white blood cells, especially neutrophils
- increased or unexplained bleeding or bruising due to a very low platelet count.