Multiple myeloma occurs when immune cells called plasma cells multiply out of control and crowd out healthy blood cells in the bone marrow. This can cause pain as it gradually begins to damage the bones and other organs of the body. About 80 percent of people with multiple myeloma develop bone disease.
Some patients will not have pain, but will have other symptoms, such as fatigue caused by anemia, or fatigue and confusion caused by high blood calcium levels or kidney failure. These are some of the first symptoms of multiple myeloma. Some symptoms indicate that a multiple myeloma patient should be treated right away; these are called the CRAB criteria:
- C stands for calcium, which can be elevated in the blood as a result of the disease.
- R stands for renal (kidney) failure, which is caused when multiple myeloma proteins damage the kidneys.
- A stands for anemia (not enough red blood cells), which is caused by the cancerous plasma cells suppressing the normal bone marrow cells.
- B stands for bone disease, which occurs when the multiple myeloma cells damage the bones, causing pain and fractures.
In the United States, about 22,000 people are diagnosed with multiple myeloma each year. It is the second most common form of blood cancer, after non-Hodgkin lymphoma.
Normal Blood Cells
Most blood cells develop in the marrow, the soft material at the center of most bones. Bone marrow contains hematopoietic stem cells, which can transform into different kinds of blood cells, depending on what kind your body needs at a particular time. When cells grow old or are damaged, they die, and new hematopoietic stem cells replace them.
Each type of blood cell has a special job:
- White blood cells help fight infection. There are several types of white blood cells. For example, plasma cells are white blood cells that make antibodies. Antibodies are part of the normal immune system. They work with other parts of the immune system to help protect the body from germs and other harmful substances. Each type of plasma cell makes a different type of antibody.
- Red blood cells carry oxygen to tissues throughout the body.
- Platelets help form blood clots to control bleeding.
Multiple myeloma begins when a plasma cell becomes abnormal. These abnormal plasma cells are called myeloma cells.
Over time, myeloma cells collect in the bone marrow and may damage the solid part of the bone. When plasma cells collect in high numbers in your bones, the disease is called "multiple myeloma." At this stage, bone damage leads to easily broken bones, or the cancerous plasma causes the bone to release excess calcium into the blood.
Multiple myeloma plasma cells make too many of one kind of antibody called monoclonal or M proteins. These can accumulate in the blood, urine, and organs, causing harm to other tissues and organs, particularly the kidneys.
In some patients, too many plasma cells of one type are made, but not to the point where a tumor forms or CRAB criteria are present. This is a benign (non-cancerous) condition known as monoclonal gammopathy of undetermined significance (MGUS), in which abnormal plasma cells make M proteins but do not cause organ or bone damage. Over time, some people with MGUS will eventually develop multiple myeloma or another blood disease. There are certain features of MGUS that put some patients at higher risk for developing multiple myeloma. Roswell Park provides laboratory testing that can identify people who have that risk.
When the body makes too many abnormal plasma cells, several conditions can develop:
- Anemia, causing fatigue and weakness
- Easy bruising or bleeding
- Frequent infections and poor healing from infection
- Bone pain, usually in the back and ribs
- Broken bones, often in the spine
- Feeling very thirsty
- Weight loss
- Nausea or constipation
- Frequent urination
It is important to note that sometimes these symptoms can be due to other problems that are not related to cancer, so it’s important to see your doctor right away for an evaluation and testing.