Multiple myeloma is a type of blood cancer caused by abnormal plasma cells in the bone marrow. (Bone marrow is the spongy tissue found inside the inner part of bones.) Plasma cells help produce antibodies that help fight infections, viruses, and bacteria.
In an autoimmune condition, the body mounts a defensive inflammatory response that targets its own tissues. Many chronic inflammatory diseases increase a person’s risk of developing blood cancers and other blood diseases. Experts have also found that autoimmune disorders can specifically be associated with the uncontrolled, rapid growth of plasma cells. And still more experts point out a misfiring immune system may allow abnormal plasma cells to grow and become cancerous. When that happens, ultimately a person’s immune system weakens and their risk of myeloma increases.
The underlying cause of the majority of multiple myeloma remains unknown. However, some risk factors have been identified: age, family history, male gender, and certain environmental factors. And, since the 1960s, researchers have observed links between autoimmune diseases and the development of myeloma.
Although the chain of events leading to the development of myeloma is unclear, many experts believe the answer lies in the inflammatory response that happens in someone with an autoimmune disease. It’s possible, they suggest, that certain inflammatory responses trigger the development of a specific non-cancerous condition known to be a precursor of myeloma. That condition is called monoclonal gammopathy of undetermined significance (MGUS).
Someone with MGUS develops abnormal proteins. Those abnormalities increase their risk of both bone marrow and blood diseases. Compared to the general population, MGUS is more prevalent in people with chronic inflammatory rheumatological diseases. That includes rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE or lupus), among others. However, one 20-year study of more than 1,300 people with MGUS found that each year only about 1 percent of the study’s participants went on to also be diagnosed with myeloma.
The association between RA and lupus with myeloma has been inconsistent in many studies and case reports. For example, in one study of nearly 140,000 people, researchers found those with a history of RA were more likely to have multiple myeloma. Another study noted that following a review of 44 published reports, lupus proved to be the most common autoimmune disease in people with multiple myeloma.
But other researchers found that when they considered a pool of 255 people with various autoimmune conditions alongside MGUS, there was a 60 percent lower risk for those with RA or lupus to develop myeloma.
All told, the evidence doesn’t add up to justify specifically naming RA and lupus as risk factors for myeloma. There still may be a common genetic or environmental susceptibility for these autoimmune diseases and MGUS. But more research is needed to understand their roles in the development of myeloma.
In an Austrian study that included nearly 3,000 people with both MGUS and a rheumatological disease (or other autoimmune condition), researchers found interesting overlaps. They observed that someone’s chance to develop multiple myeloma might vary based on the type of autoimmune condition they may have. In particular, people with spondyloarthritis (SpA), gout, or polymyalgia rheumatica showed a greater risk of progressing to myeloma. As for those with Sjögren syndrome, mixed connective tissue disease, or systemic sclerosis, there appeared to be no increased risk.
One systematic review of scientific literature looked at 32 studies that had been screened to include any one of 50 different autoimmune conditions. Researchers found people with an autoimmune disease were 13 percent more likely to develop myeloma and 42 percent more likely to develop MGUS. However, only people with one particular autoimmune condition — pernicious anemia — showed an increased risk of having both MGUS and multiple myeloma.
A separate review included 18 prior studies that covered the possible connections between RA and myeloma. Those reports revealed that having ankylosing spondylitis (AS) increased a participant’s risk of multiple myeloma by as much as 2.30 times. Having seen that, researchers concluded that, indeed, AS might be a potential risk factor for myeloma. Additional research also reported a possible overlap in the amount of people who have myeloma and as well as certain viral infections (like HIV) and/or rare autoimmune conditions (pure red cell aplasia, immune thrombocytopenia, autoimmune neutropenia, and more).
It is important to remember that not all autoimmune diseases are the same. Each has its own unique and complex pathways and mechanisms. However, current research suggests that certain autoimmune diseases may indeed play a role in the uncontrolled plasma cell growth that can lead to the development of myeloma. The takeaway? More large-scale studies are needed to clarify the roles of autoimmune conditions in the development of myeloma.
There has been a dramatic improvement in the treatment options — and survival rates — for myeloma over the last decade. And some of the research that led to those improvements focused on whether autoimmune conditions might affect a person’s myeloma treatment or outcome. One such review of scientific literature included a pool of 44 published papers. (Each paper had noted some overlap between 25 different autoimmune conditions and myeloma.) One interesting conclusion the scientists drew: In general, the majority of a person’s autoimmune symptoms went away or at least improved when they were treated for their myeloma.
A different study seemed to counter that finding. In it, researchers looked at the various outcomes of 255 people living with both MGUS and an autoimmune condition. They found that the glucocorticoids used to treat autoimmune conditions did not affect the potential progression of MGUS to myeloma.
And on the other end of the spectrum, other reports have concluded that autoimmune treatments may actually have a poor effect on someone’s risk for myeloma. For instance, there is evidence that suggests an increased risk of myeloma for those whose autoimmune disease treatment included steroids. It’s also been reported that some immunosuppressive drugs may reduce the immune system’s ability to attack cancerous cells.
Ultimately, more large-scale studies looking at high-risk autoimmune conditions and the connections to myeloma and myeloma treatment are needed.
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