Normally, new plasma cells are produced to replace old, worn-out cells in an orderly, controlled way. However, in myeloma, the process gets out of control and large numbers of abnormal plasma cells (myeloma cells) are produced. These fill up the bone marrow and interfere with the production of normal white blood cells, red blood cells and platelets.
The myeloma cells usually produce a large amount of a single type of abnormal antibody (immunoglobulin). This is known as aparaprotein or M protein. It can't fight infection effectively and often reduces the production of normal antibodies.
Myeloma cells can spread throughout the bone marrow.
Too many plasma cells can damage the bone, which causes bone thinning, pain and sometimes fractures. An area of damaged bone is known as a lytic lesion.
Symptoms of Myeloma
Myeloma may not cause any symptoms in the early stages of the disease.
Occasionally, it is diagnosed following a routine blood test before any symptoms develop.
When symptoms do happen, they are mostly caused by a build-up of abnormal plasma cells in the bone marrow, and by the presence of the paraprotein in the blood.
The most common symptom of myeloma is bone pain.
About 70% of people (7 in 10) complain of lower back pain, or pain in their ribs. The pain happens because too many abnormal plasma cells are crowding out the bone marrow, which can damage the bone. Other bones may be affected too, such as the skull or pelvis.
These may include:
- tiredness and fatigue due to a lack of red blood cells (anaemia).
- kidney problems, which are caused by the paraproteins produced by the myeloma cells. They can also cause tiredness and anaemia.
- repeated infections, particularly chest infections, due to a shortage of normal antibodies.
- loss of appetite, feeling sick, constipation, depression and drowsiness, which are caused by too much calcium in the blood (hypercalcaemia).
- unexplained bruising and abnormal bleeding, for example, nosebleeds or bleeding gums, due to a reduced number of platelets in the blood.
- weight loss.
If you have any of these symptoms, it's important to see your doctor as soon as possible. But remember, many of these symptoms can occur in other conditions - most people with these symptoms won't have myeloma.
*Information provided by Macmillan cancer support