What is myeloma?

Myeloma is a cancer of plasma cells in the bone marrow. Bone marrow is a spongy material inside our bones. The main bones it’s in are the hip bones, breastbone, arm bones, leg bones, ribs and spine. Bone marrow is part of the immune system, which protects us from infection and disease.

Bone marrow and stem cells

Bone marrow produces stem cells. These are immature cells that develop into three different types of blood cell:

  • red blood cells, which carry oxygen to all the cells in the body
  • platelets, which help the blood to clot and control bleeding
  • white blood cells, which fight infection.
Bone marrow producing stem cells
Bone marrow producing stem cells

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Plasma cells

Myeloma affects a type of white blood cell called plasma cells. Plasma cells make immunoglobulins, which are also known as antibodies. These immunoglobulins circulate in the blood and attack any viruses and bacteria in the body. If there is an infection, the bone marrow produces more plasma cells and immunoglobulins to attack whatever is causing the infection.


The immunoglobulins produced by plasma cells are made up of proteins, which are linked together to make ‘chains’. Some immunoglobulins are large protein chains, known as ‘heavy’ chains. Others are smaller chains, known as ‘light’ chains.

An immunoglobin
An immunoglobin

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There are five types of heavy chain. They are called IgG, IgA, IgD, IgE and IgM. The ‘Ig’ means immunoglobulin. There are two types of light chain. They are called kappa and lambda. Each immunoglobulin is made up of two heavy and two light chain proteins.

Plasma cells and immunoglobulins in myeloma

Normally, new plasma cells replace old, worn-out cells in a controlled way. But in people with myeloma, the process gets out of control and large numbers of abnormal plasma cells (myeloma cells) are produced. Myeloma cells can develop wherever there are plasma cells. They can spread throughout the bone marrow to several different parts of the body. This is why myeloma is sometimes called multiple myeloma.

The myeloma cells fill up the bone marrow and interfere with the production of normal white blood cells, red blood cells and platelets. They can also damage the bone and cause bone thinning, pain and sometimes fractures. An area of damaged bone is often called a lytic lesion.

Myeloma cells usually only produce one type of abnormal immunoglobulin. This is called a paraprotein or M protein. This immunoglobulin can’t fight infection and it often reduces the number of normal immunoglobulins made.

Most of the problems related to myeloma are caused by:

  • myeloma cells in the bone marrow
  • a low number of normal blood cells
  • immunoglobulins (paraproteins) or light chains in the blood and urine.

Back to Understanding myeloma

Types of myeloma

There are different types of myeloma. There are also other conditions that affect plasma cells which are related to myeloma.

Symptoms of myeloma

Myeloma may not cause any symptoms in the beginning, but they can develop over time.