Free light chains are small pieces of protein floating in the blood of people with light chain multiple myeloma.

Antibodies are proteins that are usually made up of two heavy chains and two light chains. In people with light chain multiple myeloma, the body produces too many light chains, and they can’t bind together to form antibodies.

Light chain myeloma is a less common type of multiple myeloma. About 20 percent of people with myeloma are diagnosed with this type.

In this article, we’ll explain what light chains are and what they mean for a multiple myeloma diagnosis. We’ll also cover the symptoms, treatment, and prognosis for light chain multiple myeloma.

What Are Light Chains in Multiple Myeloma?

Antibodies are specialized immune system proteins that help the body fight infection. Light chains are fragments of these proteins.

Multiple myeloma begins in the bone marrow, where the body makes white blood cells. One type of white blood cell is called a plasma cell.

Plasma cells produce antibodies, also known as immunoglobulins, that help eliminate dangerous bacteria and viruses.

People diagnosed with multiple myeloma have abnormal plasma cells that don’t work properly. Instead, they produce dysfunctional immunoglobulins that harm the body. These abnormal immunoglobulins are called monoclonal proteins, or M proteins.

Normal immunoglobulins are shaped like a Y, with four pieces linked together — two longer “heavy” chains and two shorter “light” chains. M proteins have too many of one of these types or combinations of chains.

People with light chain myeloma produce only the light chain part of abnormal immunoglobulins. These are also known as Bence-Jones proteins.

There are two types of light chains — kappa and lambda.

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Light vs. Heavy Chains

Most cases of multiple myeloma are heavy chain myeloma. In this type, the only abnormal immunoglobulin proteins are the heavy chains — the proteins that form the stem of the Y.

An even rarer type is nonsecretory myeloma, in which the body makes no abnormal proteins.

What Do Light Chains Mean in Diagnosing and Monitoring Multiple Myeloma?

Your hematologist or oncologist will likely run several tests to learn if you have light chain multiple myeloma. The tests used to detect light chain multiple myeloma are the same as those used to detect multiple myeloma generally. Your doctor might order:

• Blood tests to detect M proteins that can indicate the aggressiveness of multiple myeloma
• Urine and blood tests to check kidney function and find abnormal proteins
• Bone marrow biopsy to look for cancer cells
• Imaging tests such as X-rays, MRI, positron emission tomography, and CT scans to see damage to the bones or other organs

To diagnose light chain multiple myeloma, a blood test called serum-free light chain must show a particular level of excess light chains. Urine tests may also confirm the presence of light chains.

When reviewing your blood test results, your doctor will assess the kappa/lambda ratio of your free light chains. A high ratio means that your body has made an unusually high number of one type of free light chain.

Your healthcare team will continue to monitor your kappa/lambda ratio during multiple myeloma treatment. Free light chains have a very short life, so your doctor can track them to find out how well your body is responding to treatment.

Symptoms of Light Chain Multiple Myeloma

For the most part, light chain multiple myeloma symptoms are similar to general symptoms of multiple myeloma. These may include:

• Bone lesions — Multiple myeloma affects the bone marrow, and about 80 percent of people will experience bone damage, often in the spine, pelvis, or ribs. Symptoms can include bone pain and fractures.
• Gastrointestinal problems — Bone damage causes calcium to leak out into the blood, causing hypercalcemia (high calcium levels). This can lead to uncomfortable symptoms like stomach upset and diarrhea.
• Urinary changes — Hypercalcemia may cause you to need to urinate more.
• Neurological symptoms — Severe hypercalcemia may cause changes in your mental state, like confusion or drowsiness.
• Anemia and leukopenia — People with multiple myeloma may have low levels of red blood cells (anemia) and white blood cells (leukopenia). Symptoms may include fatigue, weakness, and frequent infections.

Kidney Damage

One common effect of light chain multiple myeloma is kidney damage and kidney failure, when the kidneys stop working effectively. About 40 percent of people with myeloma also have kidney problems at the time they’re diagnosed with the blood cancer. People with light chain myeloma are much more likely to experience kidney failure than those with non-light chain myeloma.

The kidneys have tiny filters called glomeruli that remove waste materials from blood and send them into urine. Because light chains are so small, they circulate easily in the bloodstream. When excess light chains enter the glomeruli with the blood, they mix with other proteins, clog the filters, and cause swelling and injury to kidney tissue.

Over time, the buildup of light chains can cause permanent damage and kidney failure. Symptoms of kidney failure can include:

• Urinary changes
• Fatigue
• Nausea
• Swollen feet and ankles
• Itching
• Shortness of breath
• High blood pressure

How Is Light Chain Multiple Myeloma Treated?

The goal of light chain multiple myeloma treatment is to lower the number of free light chains in the blood.

Treating light chain multiple myeloma can be complicated by the light chains’ tendency to cause kidney damage. As many as 15 percent of people require hemodialysis (removal of wastes and water from blood) to help their kidneys function at the time they’re diagnosed with myeloma, according to the Clinical Journal of the American Society of Nephrology.

Doctors may recommend a treatment plan with drugs from different classes, including proteasome inhibitors, immunomodulators, steroids, and traditional chemotherapy.

Prognosis for Light Chain Multiple Myeloma

For people diagnosed with multiple myeloma between 2016 and 2022, the five-year survival rate (percentage of people still alive after five years) is 63.7 percent. This statistic applies to people with multiple myeloma in general.

For people with light chain myeloma, survival may be shorter, perhaps by as much as two years. Doctors believe this is likely due to kidney damage caused by light chains.

Kidney damage increases your risk of several health problems, including high blood pressure (hypertension). People with kidney damage from light chain multiple myeloma often need dialysis treatment and blood transfusions. All of these factors can affect life expectancy.

Talk Openly With Your Doctor

Talk with your doctor about your risk factors and prognosis. If you have trouble sticking to your myeloma treatment regimen, be open with your oncology team about these issues. They can help you find ways to stay on track with your treatment plan.

You can also ask your oncologist if there are any promising clinical trials you might be eligible to join.