Myeloma – also known as multiple myeloma or myelomatosis – is a cancer of plasma cells in the bone marrow.
How myeloma develops
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 a paraprotein 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.
Types of myeloma
There are different types of myeloma, which are classified depending on the type of immunoglobulin (Ig) produced by the myeloma cells. The most common type of myeloma is IgG, where the heavy chain of the immunoglobulin is G. The least common type is IgE. The type of myeloma you have doesn’t usually affect the treatment you’re offered but it can influence how the disease will affect you. Around 1 in 3 people have a type of myeloma that produces light chains only. This is calledlight chain or Bence Jones myeloma. A rare type of myeloma called non-secretory myeloma produces little or no immunoglobulin.
Other conditions of the plasma cell
There are some other conditions that affect the plasma cells and are related to myeloma. They can sometimes develop into myeloma. The two most common are MGUS (monoclonal gammopathy of unknown significance) and smouldering myeloma, which is also known as indolent or asymptomatic myeloma. If you’re diagnosed with either of these conditions, you’ll be monitored with blood tests, but may not need to have any treatment unless the condition progresses and becomes an active or symptomatic myeloma. Our section on MGUS has further information. Sometimes, abnormal plasma cells are found in a bone in only one area of the body. This condition is known as a solitary plasmacytoma. It’s treated with radiotherapy. Some people with solitary plasmacytoma may go on to develop myeloma, so you’ll be regularly monitored with blood tests. Doctors don’t know what causes myeloma but a number of things are known to increase the risk of developing it.
The risk of myeloma increases with age. It’s rare in people under 40 and is most commonly diagnosed after the age of 65.
Myeloma is twice as common in African-Caribbean people than in white people.
Myeloma is slightly more common in men than women.
People who have been exposed to high levels of radiation may have a higher risk. This includes people who work in the nuclear power industry.
People who have a close family member with myeloma have a slightly increased risk of developing it.
It has been suggested that people in certain jobs have an increased risk of myeloma, possibly due to exposure to harmful substances. These include jobs in rubber manufacture, farming, painting and decorating, wood-working, hairdressing and the petro-chemical industries. However, there is very little evidence to support the claim that these occupations carry an increased risk of myeloma.