What is the Bence Jones Protein?

The Bence Jones protein (BJP) has played an important role in understanding and diagnosing multiple myeloma and other plasma cell disorders. 

This protein was first described in 1854 by Dr. Henry Bence Jones. He tested the urine of a patient who had vague, continuous pain in the chest, back, and pelvis.  The Bence Jones protein is a  free light chains, a part of antibodies normally made by plasma cells. When produced in large amounts, these light chains spill into the urine and can be detected with specialized laboratory tests. 

What is Bence Jones protein?

Bence Jones protein or BJP refers to free light chains of antibodies that circulate in the blood and may appear in the urine. Normally, the kidneys filter and process these proteins. However, when light chains are produced in excess, the kidneys cannot absorb them all, and they pass into the urine. Urine does not normally contain Bence Jones protein,  and it can be an early indicator of plasma cell disorders such as multiple myeloma.

Bence Jones protein vs. monoclonal protein to diagnose multiple myeloma

Monoclonal protein (often called M-protein, M-spike or paraprotein) is an abnormal antibody or antibody fragment produced by a single clone of plasma cells. It can consist of both heavy chains and light chains. Bence Jones protein is different because it represents only the light chain portion of the antibody without the heavy chain.

Both show abnormal plasma cell activity, but they are detected differently and provide unique information. Read how machine learning can predict progression with M-protein analysis here.  

How Bence Jones protein is detected

Standard urine dipstick tests do not detect Bence Jones protein because they only measure albumin, another type of protein. Instead, it is found using specialized methods such as immunofixation electrophoresis (IFE) or serum free light chain (FLC) assays. These tests can measure whether there are too many kappa or lambda light chains and whether the ratio between them is abnormal. In many cases, both urine and blood tests are needed for a clear picture.

Why do I need a Bence Jones protein test?

Testing for Bence Jones protein is usually recommended when there are signs of plasma cell disorders. These symptoms include:

• Persistent fatigue or weakness
• Unexplained weight loss or loss of appetite
• Bone pain, especially in the back or ribs
• Repeated infections
• Numbness or burning pain from nerve involvement
• Bone fractures or collapse of vertebrae
• Anemia, high calcium levels, or kidney problems

These symptoms are not unique to multiple myeloma or other plasma cell disorders, but they help guide healthcare providers to order Bence Jones protein testing.

Too much Bence Jones protein can damage kidneys, affecting how they filter blood and handle essential nutrients. Monitoring Bence Jones protein levels in urine tests can contribute to an early diagnosis and provide insight into kidney health and disease progression.

A bone marrow examination may be ordered to confirm abnormal plasma cells. After a diagnosis, changes in urinary Bence Jones protein levels help assess how well therapy is working. For example, a significant reduction in urinary light chains is a positive indicator of treatment response.

If you experience unexplained fatigue, bone pain, or repeated infections, talk with your care team about whether Bence Jones protein testing is appropriate. 

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Source: NIH Bence-Jones Protein