In multiple myeloma, cells inside the bone marrow called plasma cells become cancerous.

Bone marrow is the spongy tissue found at the centre of some bones. It produces the body's blood cells.

Plasma cells are normally produced in a controlled way. In cases of multiple myeloma, large numbers of abnormal plasma cells are produced. These fill up the bone marrow and interfere with the production of other cells, such as red and white blood cells.

The exact reason why this happens is unknown, but multiple myeloma is closely associated with a condition called monoclonal gammopathy of unknown significance (MGUS), and there are certain things that can increase your risk of developing it.

Monoclonal gammopathy of unknown significance (MGUS)

In almost all cases, multiple myeloma occurs in someone who previously had MGUS.

MGUS is the name for having an excess number of protein molecules called immunoglobulins in your blood. This does not cause any symptoms and treatment is not required.

However, every year around 1 in every 100 people with MGUS go on to develop multiple myeloma. There is no known way to delay or prevent this, so ongoing outpatient tests to check for cancer will usually be recommended if you have MGUS.

Other factors

As well as MGUS, certain things can increase your risk of developing multiple myeloma, including:

  • age – your risk of developing multiple myeloma increases as you get older; most cases are diagnosed at around the age of 70, and cases affecting people under 40 are rare
  • gender – men are more likely to develop multiple myeloma than women
  • ethnicity – multiple myeloma is about twice as common in black populations compared with white and Asian populations

It has also been suggested that having a family history of MGUS or multiple myeloma, having reduced immunity (for example, because of medication or HIV), being overweight or obese, and being exposed to radiation or certain chemicals may increase your risk of multiple myeloma. However, a link between these factors and the condition is less clear.

Page last reviewed: 16/02/2015
Next review due: 27/02/2018