Myeloma – the basics

What is myeloma? 

Myeloma, also known as multiple myeloma, is a type of bone marrow cancer arising from plasma cells, which are normally found in the bone marrow. In myeloma, the DNA of a plasma cell is damaged causing it to become malignant or cancerous. These abnormal plasma cells are known as myeloma cells.

Unlike many cancers, myeloma does not exist as a lump or tumour. Instead, the myeloma cells normally divide and expand within the bone marrow.

Myeloma affects multiple (hence ‘multiple myeloma’) places in the body where bone marrow is normally active in an adult. The areas most commonly affected include the bones of the middle or lower back, the hips and the rib cage. The long bones of the upper arms and legs can also be affected.

What causes myeloma?

The exact cause or causes of myeloma are unknown. There are a number of suspected risks or trigger factors such as: exposure to certain types of industrial and agricultural chemicals (with benzene being a main suspect), exposure to high doses of radiation, viruses and a weakened immune system. However, in most cases, people who develop myeloma have no clear risk factors and myeloma may be the result of several factors acting together.

As it is more common to develop myeloma later in life, it is thought that susceptibility may increase with the ageing process, and the consequent reduction in immune function, or that myeloma may result from a lifelong accumulation of toxic trigger factors which cause damage to the DNA in the cells.

There is a rare tendency for myeloma to occur in families, but the likelihood is very low. When myeloma occurs more than once within a family it is more likely to be because of exposure to similar risk and / or trigger factors.

What is paraprotein?

Paraprotein (M Protein) is the abnormal protein produced by myeloma cells and can be evident in blood and / or urine. The paraprotein structure is made up of two heavy chains and two light chains.

Paraprotein is an important marker of myeloma activity and a good indicator of response to treatment. It is usually the case that the amount of paraprotein is proportionate to the number of myeloma cells, i.e. the more myeloma cells, the more paraprotein. It is worth bearing in mind that each laboratory will have its own way of measuring and reporting test results, including the paraprotein result.

Some myeloma patients do not produce paraprotein (about 1%) and other ways of measuring myeloma need to be used such as monitoring the healthy blood cells and regular scans. These patients have what is known as non-secretory myeloma.

What are free light chains?

In multiple myeloma, abnormal plasma cells release one type of antibody (immunoglobulin) known as paraprotein. In most myeloma patients these abnormal antibodies are made up of both light and heavy chains. However, in about 20% of patients, the myeloma cells produce light chains only (no heavy chains at all).

These ‘free light chains’ can be detected in blood or in urine. This is what is known as ‘light chain myeloma’ or previously ‘Bence Jones’ myeloma. The two light chains are given the Greek names kappa and lambda, and a myeloma patient would produce either one or the other.

Free light chains can block the very fine tubules within the kidneys, and, in large amounts, can be toxic to the kidneys. It is therefore particularly important for patients with light chain myeloma to drink plenty of fluids to keep the kidneys well flushed.

What is the SFLC test?

The Serum Free Light Chain (SFLC) test measures the amount of kappa and lambda light chains and their ratio; it is used in the diagnosis of myeloma and to monitor either response to treatment or progression of myeloma.