Doctors can classify multiple myeloma in several ways. They often determine the type based on which immunoglobulins are overproduced.

Multiple myeloma is a cancer of the plasma cells. Plasma cells are found in the bone marrow. They help your body produce immune system proteins, also known as immunoglobulins or antibodies, that target and destroy pathogens. Pathogens are disease-causing organisms.

With multiple myeloma, plasma cells multiply too quickly. They overproduce an irregular protein called a monoclonal protein (M protein). Unlike a healthy immune system antibody, this protein cannot fight pathogens.

Common symptoms of myeloma include bone pain, fatigue, and nausea, but not everyone experiences them. This article overviews multiple myeloma types and subtypes and their features.

Smoldering multiple myeloma (SMM) is a precancerous condition that can develop into multiple myeloma over time.

People with SMM don’t have symptoms, so they’re not likely to know they have it. Indeed, most cases are detected incidentally.

For example, a doctor might notice increased protein levels during a routine blood or urine test and discover SMM upon further testing.

If you have SMM, you may not require any treatment. A doctor might suggest regular monitoring to look for signs of your condition progressing to active myeloma.

How often does smoldering multiple myeloma become active?

Most cases of SMM eventually progress to active multiple myeloma. According to research cited in a 2022 article:

  • SMM carries a 50% risk of progressing to myeloma within 5 years.
  • SMM carries a 65% risk of progressing to myeloma within 10 years.
  • About 25% of people with SMM never develop myeloma symptoms.

Still, the risk can vary a lot from person to person. Higher M protein levels and bone marrow plasma cell percentages carry a higher risk of progression to myeloma within a few years.

In contrast to healthy plasma cells, myeloma cells only produce one type of immunoglobulin, resulting in a surplus of that type.

Myeloma is categorized according to the type of immunoglobulin that’s overproduced. There are five types:

  • IgG myeloma: This is the most common type. In a 2020 study including 8,468 people with myeloma, about 57% had IgG.
  • IgA myeloma: In the same study, IgA accounted for 20% of myeloma cases. According to 2020 research, IgA may have lower long-term survival rates than IgG.
  • IgM myeloma: While similar to IgG and IgA, this type is much rarer, making up only 1% of myeloma cases. Overproduction of IgM usually develops into other disorders, like Waldenstrom macroglobulinemia.
  • IgD myeloma: This rare type accounts for less than 2% of myeloma cases. It’s more common in males and more likely to start at a younger age. It’s typically more aggressive.
  • IgE myeloma: Only 0.1% of myeloma cases are IgE, making it the rarest type. It’s more aggressive than other types and has lower survival rates.

Light-chain myeloma is the third most common type of multiple myeloma after IgG and IgA. It makes up about 15% of myeloma cases, according to a 2018 review.

The term “light chain” refers to the structure of immunoglobulins, which have two larger heavy chains and two smaller light chains.

In light-chain myeloma, myeloma cells produce incomplete immunoglobins that do not have heavy chains. They only have light chains, also known as Bence-Jones proteins.

Nonsecretory myeloma is a rare form of myeloma that accounts for around 3–5% of cases. It occurs when cancerous myeloma cells are present in the bone marrow but don’t make or release any immunoglobulins.

This type of myeloma is sometimes more challenging to detect since it doesn’t cause elevated levels of immunoglobulins in urine or blood.

Doctors may use bone marrow scans, such as CT scans or PET scans, to make a diagnosis.

Myeloma is a type of plasma chain or plasma cell disorder. That means it affects plasma cells’ ability to produce immunoglobulins or antibodies.

Related plasma chain disorders include:

MGUS

Monoclonal gammopathy of undetermined significance (MGUS) is a relatively common condition in which M proteins are present in your blood without affecting your health.

Different countries have reported MGUS rates ranging from 0.05–6.1%. It’s more common among certain groups, such as older adults and Black people.

MGUS doesn’t usually cause symptoms. Only around 1% of people who have it go on to develop active myeloma each year.

Doctors typically suggest monitoring MGUS with regular blood tests.

Solitary plasmacytoma

A plasmacytoma is a plasma cell tumor. Most plasma cell tumors, including myeloma tumors, grow in the bone marrow.

Multiple myeloma causes many tumors in bone marrow all over the body. In contrast, solitary plasmacytoma only causes one tumor.

Because solitary plasmacytoma is limited to a single area, it’s easier to treat. Doctors can usually remove the tumor via radiation, surgery, or both.

Extramedullary plasmacytoma

Extramedullary plasmacytoma occurs when a single plasma cell tumor grows in soft tissue rather than bone. In a 2022 study, 62% of these tumors were in the head and neck area.

As with solitary plasmacytoma, the cancer is localized to a single area, and treatment with radiation or surgery is usually effective.

Light-chain amyloidosis

Light-chain amyloidosis is when light-chain proteins produced by abnormal plasma cells accumulate throughout the body. These deposits, known as amyloid deposits, can lead to organ damage.

This condition can occur independently of myeloma cancer. However, it can also be a complication of multiple myeloma.

Waldenstrom macroglobulinemia

Waldenstrom macroglobulinemia (WM) is a rare form of cancer that shares features in common with multiple myeloma.

WM cells overproduce IgM, an M protein that’s sometimes overproduced in myeloma. Despite this similarity, experts classify WM as a type of non-Hodgkin’s lymphoma because it affects the lymphatic system.

Hyperdiploid vs. hypodiploid myeloma

Doctors sometimes classify multiple myeloma tumors according to the number of chromosomes found in tumor cells:

  • Hyperdiploid myeloma tumors have 47–74 chromosomes.
  • Hypodiploid myeloma tumors have 44 or fewer chromosomes.

The authors of a 2021 case report cite research suggesting that hyperdiploid multiple myeloma is typically less aggressive than the hypodiploid type.

What is the most common type of multiple myeloma?

Accounting for more than 50% of all myelomas, IgG is the most common type of multiple myeloma. The next most common types are IgA and light-chain myeloma.

What is the most aggressive type of multiple myeloma?

According to a 2020 study, IgA and light-chain myeloma are associated with poorer overall survival than other common types. The median overall survival was 4.7 years after diagnosis for people with IgA myeloma and 4.8 years after diagnosis for people with light-chain myeloma.

The Canadian Cancer Society reports that IgE is the most aggressive type of myeloma. However, it is extremely rare.

What is the difference between kappa and lambda multiple myeloma?

Kappa and lambda are two types of light chains. In multiple myeloma, one or the other may be overproduced. According to a 2017 study, myeloma with lambda light chains carries a poorer overall outlook.

Multiple myeloma is a cancer that causes uncontrolled plasma cell growth. The hallmark of myeloma is the presence of M proteins in blood or urine. The type of M protein overproduced determines the type of myeloma.

The most common types of myeloma include IgG myeloma, IgA myeloma, and light-chain myeloma. If you receive a myeloma diagnosis, your doctor can help you learn more about your type and what it means.