What Is Myeloma?
Accounting for around 10% of blood cancer cases, myeloma is a relatively rare disease that develops in plasma cells — the white blood cells that grow in bone marrow. Myeloma most often affects people who are aged 65 and older. Although myeloma grows within bone, it is not considered bone cancer.
Annually, more than 30,000 people in the United States are diagnosed with myeloma.
Parts of the body involved in myeloma include:
- Bone marrow: Spongy blood-producing tissue inside the bones, where all of the blood in the body is produced and where malignant (abnormal) plasma cells grow
- Plasma cells: Produced in the bone marrow and a part of the immune system, these are types of white blood cell that play an important role in creating antibodies that fight infection. In myeloma, plasma cells are abnormal.
- Immunoglobulins: Another word for antibodies, these proteins are produced by plasma cells to form a crucial part of your immune response. They bind to infectious agents, like bacteria or viruses, which identify them for destruction by other immune system cells.
- Bone cells: Specifically, osteoblasts that make bone and osteoclasts that dissolve bone. Myeloma cells produce a substance that stimulates the breakdown of bone by osteoclasts and inhibits the activity of osteoblasts, producing holes in the bone called “lytic lesions.”
- The nervous system can cause myeloma. Nerve damage may lead to the toxic, abnormal proteins produced by myeloma cells.
Stages of Myeloma
Multiple myeloma is staged based on four factors according to the Revised International Staging System:
- Stage 1: At this point, the amount of beta-2 microglobulin is less than 3.5 mg/L, albumin level is 3.5 g/dL or greater, cytogenetics (specific gene abnormalities) are considered not high-risk and lactate dehydrogenase levels are normal.
- Stage 2: Beta-2 microglobulin is between 3.5 and 5.5 mg/L and other factors.
- Stage 3 and 4: At these stages, beta-2 microglobulin is 5.5 mg/L or greater, cytogenetics are considered high-risk and LDH levels are high.
Types of Myeloma
There are several types of myeloma — all related yet appearing and acting differently in the body. While myeloma is a rare disease overall, the most commonly diagnosed is multiple myeloma:
Multiple myeloma is a cancer of plasma cells that affects several areas of the body, and is found in 90 percent of diagnosed cases. A tumor that grows from cancerous plasma cells is called a plasmacytoma. Isolated plasmacytoma is diagnosed when a single tumor grows, while multiple myeloma is diagnosed when more than one plasmacytoma develops. Plasmacytomas most often begin developing in the bone marrow, eventually spreading through the cavity containing the marrow and later the bone itself.
Multiple Myeloma Subtypes
- Light chain multiple myeloma: Diagnosed when myeloma cells produce damaged, incomplete antibodies called immunoglobins. These proteins build up and harm the kidneys.
- Nonsecretory myeloma: When tested, this subtype shows multiple myeloma cells that don't release the abnormal proteins characteristic of myeloma into the blood or urine. It may require more frequent bone marrow biopsies to monitor this disease.
- Rarer types of multiple myeloma: These include immunoglobulin D (IgD) myeloma and immunoglobin E (IgE) myeloma
Similar to myeloma, amyloidosis is a disease caused by defective plasma cells producing too much protein, but the protein affects areas of the body that are different from myeloma — such as the heart, kidneys and digestive system. Because what is underlying the two diseases is similar, this condition is sometimes treated with some of the same therapies as myeloma, including certain drug therapies and stem cell transplantation.
Rarer Forms of Myeloma
- Plasmacytoma: A solitary tumor made up of cancerous plasma cells, plasmacytoma often begins in the bone but can develop in other organs such as the skin and lungs. Over time, plasmacytomas may lead to multiple myeloma.
- Multiple solitary plasmacytoma: This type of myeloma involves multiple tumors but does not have some of the other features of multiple myeloma, such as bone disease, and the bone marrow appears normal.
- Extramedullary myeloma: A disease involving organs besides the bone, such as the skin, throat, lungs and muscle
How Myeloma Develops
Myeloma develops when plasma cells — infection-fighting blood cells in the immune system — become abnormal and grow and divide uncontrollably to become tumors.
During a normal immune response, B cells mature and change into healthy plasma cells. Those plasma cells then create antibodies that help the immune system recognize and fight the infection.
Myeloma occurs when a damaged B cell develops into an abnormal plasma cell. Instead of helping the immune system fight disease, myeloma cells, which have no real purpose in the body, grow quickly and crowd out healthy blood cells. Over time, this process can lead to conditions such as anemia (low hemoglobin) and thrombocytopenia (low platelets or blood clotting cells). Because the immune system is impaired, patients with myeloma are at increased risk of infection.
Myeloma cells produce abnormal antibodies called monoclonal proteins, or M proteins. These proteins build up in the body, leading to the health problems associated with myeloma.
Myeloma is categorized based on whether it has symptoms and how quickly it develops:
- Asymptomatic myeloma: Also called smoldering myeloma, this develops slowly and has none of the characteristic symptoms, such as bone pain or anemia or kidney damage. Patients diagnosed with smoldering myeloma also have fewer plasma cells and abnormal proteins in their bone marrow when compared with those with symptomatic nyeloma.
- Symptomatic myeloma: Also called active myeloma, this has observable symptoms, such as bone disease, kidney damage and anemia.
What Are the Symptoms of Myeloma?
There are few early warning signs of myeloma — and some people have none at all. Symptoms of myeloma that appear at diagnosis are sometimes referred to by the acronym CRAB, which stands for:
- Calcium build-up, also called hypercalcemia
- Renal (kidney) problems
- Anemia, or lowered production of red blood cells
- Bone lesions and/or fractures
As a result of these problems, some of the most common symptoms of myeloma include:
- Bone pain, unexpected fractures
- Kidney damage or failure
- Weakness and numbness
- Increased thirst
- Frequent infections
- Increase or decrease in urination
- Weight, appetite loss
Symptoms of other medical conditions may mirror some of those involved with myeloma. If you are treated for those conditions, or if your symptoms last for several weeks despite medical treatment, you may need further consultation to rule out myeloma.
What Increases Your Risk of Myeloma?
Things that put you at higher risk for getting myeloma are called risk factors. Doctors do not fully understand what causes most cases of myeloma, and even defined risk factors do not have strong associations with developing myeloma.
Age increases the risk of most cancers, including myeloma, which is most often diagnosed after age 65.
Males are more likely than females to be diagnosed.
African Americans are about twice as likely as other groups to develop myeloma.
Radiation exposure may increase risk of myeloma.
Chemicals, pesticides and exposure to other toxins like Agent Orange, asbestos and benzene may be linked to myeloma.
Chronic inflammation may be involved with myeloma. A small subset of patients (around 1%) diagnosed with a condition called MGUS, monoclonal gammopathy of undetermined significance, will develop myeloma.
Being overweight is associated with developing several cancers and, in early studies, has shown an association with myeloma.
Certain genetic factors, including abnormally developing genes, may increase risk of myeloma.
At City of Hope, our world-renowned hematopathologists perform leading-edge diagnostics to ensure the best outcomes for our myeloma patients.