What Is Myeloma?

H&E stain, light microscopy, multiple myeloma
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Myeloma is cancer of the antibody-producing white blood cells -- the plasma cells. Plasma cells develop from B-lymphocytes, or B-cells, which arise from stem cells in the bone marrow.

Myeloma, leukemia and lymphoma are the three main categories of blood cancer.

Myeloma tends to be a cancer of older individuals, with a median age at diagnosis of 69 years. The risk of developing myeloma also depends on genetic factors and race – for instance, blacks are affected by multiple myeloma 2 to 3 times more frequently than whites.

Also known as:  Multiple myeloma, or MM

Related terms: Plasmacytoma, Plasma cell dyscrasia

Signs and Symptoms:

  • Bone pain or fractures
  • Low blood counts, tiredness, dizziness and shortness of breath
  • Infection
  • Symptoms of too much calcium -- thirst, frequent urination, nausea
  • Kidney problems

The symptoms of myeloma relate in part to the impact of excess antibody procuction in the body, such as in the kidneys. Signs and symptoms also develop from overgrowth of the antibody-producing cells, which may crowd out healthy cells in the bone marrow, leading to anemia and low cell counts in the blood. This can also lead to infections, since the body’s immune function may be compromised. Myeloma can also create weakness and defects in the bones -- including so-called osteolytic lesions. As bone breaks down, calcium is released into the bloodstream.

Antibodies and M-protein in Myeloma

In a healthy person, plasma cells make antibodies, or immunoglobulins, to help fight off infection.

Antibodies are proteins that have different parts: their parts include so-called heavy chains and light chains. Normally plasma cells in the body generate a diverse portfolio of antibodies that are specific to all different targets on invaders. Immunoglobulins come in different classes (IgA, IgG, IgM, IgD, IgE).

In myeloma, however, there are mutations in a single B-lymphocyte/plasma cell, causing it to grow out of control, make copies of itself. These cancerous plasma cell clones are called myeloma cells. Myelomas secrete a single class of immunoglobulins or light chains only.

In general, the myeloma cells continue to produce the same antibodies as the original cancerous cell. This leads to an excessive amount of one type of antibody. This abnormal antibody does not function like a normal antibody to help to fight infection. The excess of one type of immunoglobulin is called monoclonal protein, or “M-protein.”

Types of Myeloma

Smoldering myeloma refers to a type that falls in between 2 related diseases: “monoclonal gammopathy of unknown significance,” or MGUS, and active multiple myeloma. Patients with smoldering myeloma do not have symptoms; in smoldering myeloma, blood tests come back worse than in MGUS but do not have the findings typical of active, symptomatic multiple myeloma. Though there is an increased level of plasma cells in the marrow and/or an elevated M-protein, there is still no anemia or damage to the bones or kidneys.

When symptoms such as anemia and bone involvement arise, the myeloma is considered symptomatic or active. The types of antibody proteins that are found in the blood further classify symptomatic myelomas. As malignant myeloma cells grow in the bone marrow, they begin to crowd the healthy cells that make new white cells, red cells and platelets. This leaves the patient with fewer red cells to carry oxygen to their organs, fewer platelets to form blood clots, or fewer white cells to fight infection.

The myeloma cells will also invade bone tissue, causing damage and areas of weakness in the bone. Plasma cells and myeloma cells release chemicals called cytokines, which also contribute to bone destruction. As a result, myeloma patients will often have characteristic bone damage called osteolytic lesions.

On images and scans, four main patterns of myeloma are recognized: Multiple well-defined "punched out" areas of bone; a more diffuse and general lack of mineral density in skeletal bone; a single large/expanding area of malignancy, commonly in a vertebrae or in the pelvis; and osteosclerosing myeloma which involves abnormal hardening of bone and an elevation in bone density.

Treatment Advances

In the last 15 years or so, quite a number of new agents have been developed and approved by the FDA for the treatment of MM. Advantages of these new agents are that they work against MM in the bone marrow but also help influence cells that are important in the disease process of MM -- such as osteoclasts, osteoblasts and immune cells. New drugs and more effective treatment of MM-related bone disease have resulted in patients reporting better quality of life.

Updated February 2016, TI.


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