Peripheral neuropathy (PN) — weakness, numbness, or pain related to nerve damage — is a common symptom of clonal plasma disorders. Some people with PN experience it as pain, numbness, weakness, or a pins-and-needles sensation. One clonal plasma disorder associated with PN is monoclonal gammopathy of undetermined significance (MGUS).
In clonal plasma disorders including MGUS, an abnormal protein known as the monoclonal protein (M protein) is present in the blood. Sometimes referred to as myeloma protein, this protein forms within the bone marrow — the blood-producing tissue in the center of most bones. Scientists have not determined what causes the protein to form, and many individuals who have MGUS don’t experience any signs or symptoms. MGUS can progress to multiple myeloma but does so at a very low rate.
If MGUS can go entirely undetected, how are individuals diagnosed with it? More importantly, if most people don’t show signs or symptoms, what does it mean if you do, and what symptoms might you experience? Here, we will take a look at the relationship between MGUS and PN, including how the two can be treated together.
There is a spectrum of clonal plasma disorders referred to as monoclonal gammopathies. They include MGUS, multiple myeloma, and Waldenstrom’s macroglobulinemia. All of these disorders are characterized by the production of M protein, a type of monoclonal immunoglobulin. The term “monoclonal immunoglobulin” refers to antibodies that are exactly the same.
M protein is present in the blood of roughly 3 percent of the general population over the age of 50. This incidence increases with age, making it relatively common. Fortunately, very few people have a malignant form, such as multiple myeloma or Waldenstrom’s macroglobulinemia.
MGUS is considered premalignant, or benign, and is the most commonly diagnosed of the disorders. However, some forms of MGUS can become malignant (cancerous). The three major types of MGUS — IgM MGUS, non-IgM MGUS, and light-chain MGUS — are associated with different types of malignancy. IgM MGUS can progress to Waldenstrom’s macroglobulinemia; non-IgM MGUS can progress to multiple myeloma; and light-chain MGUS can progress to a light-chain type of multiple myeloma. According to a long-term study from 2002, MGUS has a very small chance — 1 percent per year — of developing into one of the malignant forms.
Peripheral neuropathy is the name for any condition that involves damage to the peripheral nervous system. This large communication network sends signals between the brain and spinal cord (the central nervous system) and other parts of the body. The nerves responsible for sending the signals, known as the peripheral nerves, serve many functions, including:
The peripheral nerves are essential to keeping the body functioning normally. When these nerves are damaged, peripheral neuropathy is the result. Peripheral neuropathy can present with many neurological symptoms, including:
PN’s impact on a person’s life depends on its severity. Some individuals experience tingling in a limited area of the body, and it does not hinder them from remaining active. In the most severe cases, however, individuals with PN cannot walk at all because of the intense pain their neuropathy causes.
Individuals with MGUS face symptoms including numbness, balance issues, or tingling in their hands or feet, which often feels like pins and needles. This sensation results from peripheral neuropathy and is often the first indication that something is wrong.
Many members of MyMyelomaTeam share their experiences with peripheral neuropathy. One member wrote, “My first symptom of MGUS was numbness in my toes. My neuropathy spread from my feet to the top of my hips. I was so weak I ended up in a wheelchair. I walked with a walker or a cane for several years.”
Weakness is another common symptom of peripheral neuropathy discussed by members of the MyMyelomaTeam community. One wrote about leg weakness, saying, “The neuropathy weakens my legs and gives me pins-and-needles pain down both of my legs.”
Another member's experience with peripheral neuropathy negatively impacted more than just their physical health: “Peripheral neuropathy is the worst part for me. I was a runner and biker for years, but have had to give it up.”
A MGUS diagnosis can occur by chance, so many individuals present with peripheral neuropathy before being diagnosed with MGUS. Until the cause of the neuropathy is revealed, the condition is referred to as unexplained neuropathy.
Peripheral neuropathy is a well-recognized complication of clonal plasma disorders. If you exhibit the common risk factors for the presence of the M protein, your doctor likely will test your blood for it. Deciphering the exact cause of PN, however, might take some time: A doctor will need to rule out the possibility of multiple myeloma, Waldenstrom’s macroglobulinemia, and other plasma cell disorders — such as immunoglobulin light-chain amyloidosis and osteosclerotic myeloma. A doctor will perform certain tests to determine which monoclonal gammopathy is to blame for peripheral neuropathy.
A person living with MGUS can be expected to develop peripheral neuropathy. That said, having PN does not necessarily indicate a more severe health issue. PN can have many different causes, and it’s necessarily an indication of disease progression, especially in MGUS.
MGUS typically causes no symptoms, so detection of the condition usually happens by chance when a person’s blood is tested for other reasons. A blood test may show an increased total protein, for example. From there, a more specific blood test, known as serum electrophoresis, can identify the particular abnormality present. A doctor may order a blood test for people who are experiencing symptoms with no known cause.
A person’s PN treatment plan will depend on certain factors. If the condition causing the peripheral neuropathy can be treated (such as multiple myeloma or Waldenstrom’s macroglobulinemia), then symptoms will likely ease as the condition does.
MGUS, on the other hand, typically is not treated. Instead, MGUS is carefully monitored to make sure the condition is not progressing to a malignant form.
Certain symptoms or complications caused by MGUS can be treated, however. If a person experiences severe PN, a doctor may prescribe medication. For people with the IgM type of MGUS, intravenous immunoglobulin treatments may offer short-term relief. Unfortunately, regardless of a person’s MGUS type, there is no certainty that any current treatment will work.
If you have peripheral neuropathy from MGUS, you should ask a neurology specialist what treatment options are available for you. It is also important to attend follow-up appointments with your health care team to monitor the progression of your condition and symptoms.
MyMyelomaTeam is the social network for people with myeloma and their loved ones. Here, a community of individuals comes together to share their experiences and encouragement with others. Members frequently discuss MGUS and neuropathy pain.
Have you experienced MGUS or peripheral neuropathy with myeloma? Share your experience in the comments below or by posting on MyMyelomaTeam.