Light chain multiple myeloma is a type of multiple myeloma, a cancer of the plasma cells. Multiple myeloma begins in the bone marrow, where white blood cells are formed. When the body detects an infection, these white blood cells transform into plasma cells, which create proteins called immunoglobulins — also known as antibodies. These immunoglobulins, or Ig for short, work to eliminate dangerous bacteria and viruses. In people with multiple myeloma, plasma cells don’t work properly. Instead, they produce damaged Ig that harm the body. These damaged Ig 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 are excess quantities of one of these types or combinations of chains. About 20 percent of people with multiple myeloma are diagnosed with light chain multiple myeloma. People with light chain myeloma only produce the light chain component of abnormal immunoglobulins. These are also known as Bence-Jones proteins.
Light chain multiple myeloma symptoms are similar to symptoms of other types of myeloma.
Because multiple myeloma affects the bone marrow, about 85 percent of people with multiple myeloma will experience bone damage, often in the spine, pelvis, or ribs.
Excess calcium from bone damage, called hypercalcemia, can cause urinary issues and gastrointestinal problems like stomach upset, excessive thirst, and diarrhea.
Hypercalcemia can also cause changes in mental state such as confusion and drowsiness.
Myeloma’s effects on the bones can also cause anemia — a deficiency of red blood cells — and lowered immunity, as there are no longer enough normal white blood cells to fight infection. Anemia can cause fatigue and weakness.
One common effect of light chain multiple myeloma is kidney damage. The hypercalcemia associated with all types of multiple myeloma can damage the kidneys, but light chain variants of myeloma can be especially harmful. Because the light chains are so small, they easily circulate in the bloodstream. The kidneys contain tiny filters called glomeruli, which filter the blood and send waste materials into the urine. When excess light chains enter the glomeruli with the blood, they mix with other proteins and clog the filters. These clogs inflame and injure the kidney tissue. This damage is called light chain cast nephropathy. Over time, this buildup of light chains can cause permanent damage and kidney failure. Symptoms of kidney failure include urinary changes, fatigue, nausea, swollen feet and ankles, itching, shortness of breath, and high blood pressure.
The tests used to detect light chain multiple myeloma are the same as those used to detect multiple myeloma generally. Your doctor might order the following tests:
Blood tests can detect M proteins and other proteins that can indicate the aggressiveness of a multiple myeloma. Blood tests can also reveal low blood counts, poor kidney function, and high calcium levels.
M proteins can be detected in the urine. Testing for M proteins usually involves collecting urine over a 24-hour period.
Bone marrow cells are extracted through a long needle and examined in a laboratory for malignant cells.
X-rays, magnetic resonance imaging (MRI), positron emission tomography (PET), and computed tomography (CT) scans can all show damage to the bones or to other organs caused by multiple myeloma.
Every diagnosis of light chain multiple myeloma begins with a general diagnosis of myeloma. There are two criteria for a diagnosis of multiple myeloma, according to the International Myeloma Working Group.
The first criterion is the detection of 10 percent or more malignant plasma cells in the bone marrow, or the detection of plasmacytoma in the bones or soft tissues. Plasmacytomas are tumors made up of malignant plasma cells.
The second criterion can be met in two ways. The first is the standard CRAB criteria. CRAB is an acronym for the types of damage that multiple myeloma can inflict on the body, including:
The CRAB criteria were the gold standard for multiple myeloma diagnosis for decades. However, with improved imaging technology and biomarker testing, multiple myeloma can now be diagnosed earlier, before it causes the damage that comprises the CRAB criteria. Along with the detection of malignant cells, these new criteria that confirm a diagnosis of multiple myeloma include:
The last diagnostic criterion — a serum free light chain ratio of 100 or more — can be used to specifically diagnose light chain multiple myeloma. A blood test called the serum free light chain assay detects excess light chains in the blood. In people with light chain multiple myeloma, there will be a much higher level of kappa chains compared to lambda chains, or vice versa, because the M proteins are producing too much of one specific light chain.
Urine testing can also be helpful in detecting light chain myeloma caused by overproduction of lambda light chains. The urine protein electrophoresis test (UPEP) has been used in the past to detect light chain myeloma, but it has become less common due to expense. Light chain multiple myeloma is often diagnosed along with another condition called light chain amyloidosis (also called AL amyloidosis or primary amyloidosis). While multiple myeloma refers to the malignancies in the bone marrow, AL amyloidosis refers to the buildup of light chain proteins in the organs.
Most treatments for light chain multiple myeloma are similar to those for other forms of myeloma. Treating cases of light chain multiple myeloma can be complicated by the light chains’ tendency to cause kidney damage — 40 percent of people with multiple myeloma have kidney damage at the time of diagnosis.
For people with renal impairment, a chemotherapy drug called bortezomib (Velcade) is usually prescribed as the first line of treatment. Velcade is a proteasome inhibitor. It works by “shutting off” the cell function that lets cells dispose of excess proteins. Because malignant myeloma cells produce too many proteins, they eventually “fill up” with these excess proteins and die. Bortezomib is administered through injections or infusions and is often combined with dexamethasone, a type of corticosteroid. Corticosteroids are believed to help kill cancerous cells and can help ease side effects of chemotherapy drugs, such as nausea and vomiting. In addition to bortezomib, many other drugs have been approved for myeloma in recent years.
A type of kidney dialysis called high-cutoff hemodialysis (HCO-HD) is a newer treatment option for light chain multiple myeloma. HCO-HD is used alongside chemotherapy. Regular hemodialysis is used to help remove bodily waste that the injured kidneys can no longer remove. During HCO-HD, the blood is purified through a special membrane which is designed to trap excess light chain proteins.
Small studies have shown that high-cutoff hemodialysis may help improve kidney function in people with light chain multiple myeloma. HCO-HD is still new, and additional research is required to understand the full range of its benefits and risks.
Plasmapheresis, also known as blood exchange, can also be used to remove light chains and support chemotherapy treatment. During plasmapheresis, the liquid component of the blood is removed and replaced with plasma from a donor or with a plasma substitute. The process is usually done in a medical center or a hospital, and it takes about two to three hours.
On MyMyelomaTeam, the social network and online support group for those living with myeloma, members talk about a range of personal experiences, including light chain multiple myeloma. Do you have light chain multiple myeloma? Share your experience in the comments below or on MyMyelomaTeam. You'll be surprised how many others share similar stories.