Multiple myeloma starts with genetic changes in one plasma cell. Eventually, affected plasma cells crowd out healthy blood cells. Scientists are still unsure what causes the genetic changes.

Multiple myeloma is a cancer of the blood. This cancer occurs when plasma cells multiply rapidly, and it can eventually cause damage to your organs.

Multiple myeloma develops through precursor conditions before causing symptoms, but most people with these preceding conditions don’t develop active multiple myeloma.

Like all cancers, multiple myeloma results from changes in your genes, but it’s not passed down in families. Researchers still aren’t sure why these genetic changes occur, but several known risk factors exist.

Multiple myeloma depends on genetic changes, also called “mutations.” These particular changes appear in the structure of specific chromosomes. The mutations happen early in the development of the condition.

Even though genetic changes lead to multiple myeloma, the condition isn’t hereditary or passed down from generation to generation.

Genetics of multiple myeloma and race

Multiple myeloma is more than twice as common among Black people in the United States than among white people. Researchers continue to investigate the reasons for this disparity.

There may be a link between African ancestry and specific genetic subtypes of multiple myeloma. Other research suggests that several factors may be at play, including socioeconomic factors. More research is needed.

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Genetic changes in a plasma cell may cause it to become a cancerous myeloma cell. This single cell multiplies into several myeloma cells, which grow faster, larger, and in greater numbers. The myeloma cells build up in your bone marrow, leaving little room for healthy blood cells.

According to the Canadian Cancer Society, plasma cells typically make up 2–3% of your bone marrow. In active multiple myeloma, plasma cells may make up more than 60% of your bone marrow.

Healthy plasma cells make useful antibodies, but myeloma cells make an altered antibody called an “M-protein.” The presence of M-protein in your blood suggests a concern with your plasma cells.

Doctors can measure the amount of M-protein in your blood and the percentage of plasma cells in your bone marrow. They then can use this information to track whether multiple myeloma is developing or progressing.

MGUS vs. multiple myeloma

Multiple myeloma is one disease on a spectrum, developing after precursor conditions:

  • Monoclonal gammopathy of undetermined significance (MGUS): MGUS occurs when you have low M-protein levels and plasma cells make up less than 10% of your bone marrow. Only about 1% of MGUS cases progress to multiple myeloma each year.
  • Smoldering multiple myeloma (SMM): In SMM, M-protein levels are higher, and plasma cells make up 10–60% of your bone marrow, which usually still isn’t enough to cause signs or symptoms.
  • Active multiple myeloma: In active multiple myeloma, your M-protein and plasma cell levels are high enough to cause signs, such as:

Certain risk factors may make you more likely to develop multiple myeloma:

  • Age: While multiple myeloma can develop at any age, most cases occur in people more than 65 years of age. Only 0.4% of multiple myeloma diagnoses occur before the age of 35 years.
  • Sex: Multiple myeloma is 1.5 times more common in males than females.
  • Race: The risk of multiple myeloma is twice as high among Black Americans than white Americans.
  • Family history: Your risk is higher if you have a parent or sibling with multiple myeloma, though most people with the condition don’t have a family history.
  • Excess body weight: Excess body weight may increase your chances of developing multiple myeloma.
  • Other plasma cell conditions: Having MGUS or solitary plasmacytoma may make you more likely to develop multiple myeloma. A solitary plasmacytoma is a lone clump of cancerous plasma cells.

You may develop multiple myeloma even if you don’t have any of these risk factors. You can also have all or several of these risk factors and still not develop multiple myeloma.

Here are answers to some questions you might have about the causes and symptoms of multiple myeloma.

Does stress cause multiple myeloma?

Stress doesn’t cause multiple myeloma. But, many people with multiple myeloma experience chronic stress and depression, which are both linked to a poorer outlook for people with cancer.

Is multiple myeloma hereditary?

Multiple myeloma isn’t hereditary. The genetic factors that contribute to multiple myeloma aren’t inherited but instead arise spontaneously in individuals.

Still, having a close family member with multiple myeloma may increase your risk. In a 2019 study, people who had MGUS were more than twice as likely to have a first degree relative (parent or sibling) with multiple myeloma.

What’s the first sign of multiple myeloma?

The most common early symptoms of multiple myeloma are back or bone pain, fatigue, and recurring infections. The American Cancer Society notes that the condition can also present with no symptoms.

Can you prevent multiple myeloma?

There’s no known way to prevent multiple myeloma, and most of its risk factors are out of your control. But, some research suggests that obesity may contribute to multiple myeloma, so maintaining a moderate weight may help.

Multiple myeloma happens because of genetic changes to your chromosomes. These genetic changes first occur in a single cell, which then multiplies rapidly. Eventually, myeloma cells crowd out your healthy cells: a process that can cause serious symptoms and complications.

Scientists aren’t yet sure what causes the genetic changes that lead to multiple myeloma, but they’re aware of certain risk factors, such as race and age.

The genetic changes aren’t inherited, so the condition doesn’t usually run in families. Still, having a relative with multiple myeloma may increase your risk.