What Is Multiple Myeloma? The Basics

Multiple myeloma is a cancer that starts in plasma cells, a type of white blood cell that lives in the bone marrow. Plasma cells normally make antibodies that help your body fight infection. In myeloma, these cells grow out of control and crowd out the healthy blood cells your body needs. It is a cancer of the bone marrow, not a cancer that begins in bone itself, which is a common point of confusion.

Myeloma accounts for roughly 1 to 2 percent of all cancers in the United States and about 10 percent of all blood cancers. It is diagnosed most often in people in their mid-60s to early 70s, and it is somewhat more common in men than women. It is also about twice as common in Black Americans as in white Americans, for reasons that are not fully understood.

What Is Multiple Myeloma and How Does It Affect the Body?

Myeloma begins when a single plasma cell acquires genetic changes that make it multiply when it should not. Those abnormal cells are called myeloma cells. They build up in the bone marrow, the spongy tissue inside your bones where blood cells are made.

As myeloma cells accumulate, they interfere with normal blood cell production. That is why many people with myeloma develop anemia, which causes fatigue and shortness of breath. They can also develop low white blood cell counts, which raise infection risk, and low platelet counts, which make bleeding and bruising easier.

Myeloma cells also produce an abnormal antibody fragment called M protein. This protein can build up in the blood and, in some cases, damage the kidneys. The word “multiple” in the name refers to the fact that myeloma often affects many areas of the bone marrow at once, not just one spot.

One feature that sets myeloma apart from many other cancers: it does not usually form a solid tumor you can feel. Instead, it spreads through the marrow, which is why it is considered a cancer of the whole bone marrow system rather than a single lump.

What Are the Symptoms of Multiple Myeloma?

Symptoms are often vague at first, which is part of why myeloma can go undiagnosed for a while. Many people feel tired or notice they get sick more often, without any obvious cause.

Doctors often group the classic signs under the acronym CRAB:

• C — Calcium levels in the blood that are too high, which can cause confusion, constipation, and increased thirst
• R — Renal (kidney) problems, since the abnormal proteins can damage the kidneys
• A — Anemia, leading to fatigue, weakness, and pale skin
• B — Bone problems, including pain and fractures, most often in the back, ribs, or hips

Bone pain is common because myeloma cells release signals that activate cells called osteoclasts, which break down bone. This can cause thinning bones and, in some cases, compression fractures of the spine. That is why back pain that does not go away is sometimes the first clue.

Not everyone has these symptoms. Some people are diagnosed before they feel sick at all, often after a routine blood test shows unusual results.

How Is Multiple Myeloma Diagnosed?

There is no single test that confirms myeloma on its own. Diagnosis usually combines blood tests, urine tests, imaging, and sometimes a bone marrow biopsy.

Blood tests can measure M protein, calcium, kidney function, and blood counts. Urine tests can detect abnormal proteins that the kidneys are filtering out. Imaging tests such as X-rays, MRI, or low-dose whole-body CT scans can reveal bone damage.

A bone marrow biopsy is often the most definitive step. A doctor removes a small sample of marrow, usually from the hip bone, and a pathologist examines it under a microscope to count plasma cells. In a healthy person, plasma cells make up a small fraction of marrow cells. In myeloma, that number is higher, and the cells look abnormal.

Doctors also use these results to distinguish myeloma from a related but less serious condition called monoclonal gammopathy of undetermined significance, or MGUS. In MGUS, M protein is present but there are no symptoms, no organ damage, and no cancer-level plasma cell counts. MGUS is fairly common, especially with age, and only a small share of people with it go on to develop myeloma.

What Is the Difference Between MGUS, Smoldering Myeloma, and Active Myeloma?

Myeloma exists on a spectrum, and where a person falls on that spectrum changes what happens next. This distinction matters because it affects whether treatment is needed at all.

MGUS is a precancerous state. M protein is detectable, but there is no organ damage and plasma cells are not high enough to meet myeloma criteria. It usually requires monitoring, not treatment.

Smoldering myeloma sits in the middle. Plasma cell counts and M protein levels are higher than in MGUS, but there is still no organ damage. Many people with smoldering myeloma are watched closely rather than treated right away, though some higher-risk cases may be offered treatment earlier.

Active myeloma means the disease is causing damage — the CRAB features or other serious problems. This is when treatment typically begins.

The line between these categories is defined by specific lab values and clinical findings, which is why regular monitoring matters for anyone with MGUS or smoldering myeloma.

How Is Multiple Myeloma Treated?

Treatment for active myeloma has changed a great deal over the past two decades. It is not usually cured with standard therapy, but many people live for years with the disease under control.

Treatment often combines several types of drugs rather than using one alone. Common categories include:

• Proteasome inhibitors, which interfere with how myeloma cells break down proteins
• Immunomodulatory drugs, which change how the immune system interacts with cancer cells
• Monoclonal antibodies, which target specific markers on myeloma cells
• Corticosteroids, which are used alongside other drugs

Some people are also candidates for a stem cell transplant, usually using their own cells collected before high-dose chemotherapy. This is generally considered for people who are healthy enough to tolerate it and whose disease responds well to initial treatment.

Because myeloma is a disease of the whole marrow, treatment is typically ongoing or repeated rather than a one-time event. Many people receive continuous therapy to keep the disease suppressed.

It is worth being honest here: outcomes vary widely from person to person. Some people respond well for many years. Others have disease that returns sooner. Response depends on factors like age, overall health, the specific genetic features of the cancer cells, and how the disease responds to the first round of treatment.

What Is the Outlook for Someone With Multiple Myeloma?

The outlook for myeloma has improved substantially compared with a few decades ago, largely because of newer drug combinations. That said, it remains a serious cancer, and it is not considered curable with standard treatment for most people.

Survival statistics are often quoted, but they describe large groups of people, not any single person. They also reflect patients diagnosed years ago, before many current treatments were available. Because of that, older statistics may understate what people diagnosed today can expect.

What matters more for an individual is the specific biology of their disease, how well it responds to treatment, their age, and their other health conditions. These are the factors a doctor weighs when discussing prognosis.

Myeloma research is active, and new drugs and combinations continue to be studied. For people living with the disease, regular follow-up and open communication with a care team are central to managing it over the long term.