Types of Myeloma

Myeloma is a blood cancer that can present very differently in different people.
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Myeloma and multiple myeloma refer to the same disease. There are different types of myeloma, and these myeloma types are determined based on activity of the disease, as well as by the types of antibodies, or immunoglobulin proteins, that are being abnormally produced.

At the time myeloma is first diagnosed, there may or may not be any symptoms: people range from having no symptoms to having severe symptoms with complications that require emergent treatment.

One particular type of myeloma—monoclonal gammopathy of undetermined significance (MGUS)—produces extra antibodies at low levels, but does so without significant problems in the organs. It can develop into active myeloma, but when it does, it usually does so slowly. Not everyone with MGUS will go on to develop myeloma, but some may, which is why annual monitoring is necessary. MGUS, although it is a benign condition, runs the risk of transformation into multiple myeloma at a rate of ~1.5 percent per year.

MGUS

There are 2 major differences between MGUS and myeloma:

1. When ​cancer or another disease causes the production of abnormal levels of antibody protein , that protein is called paraprotein. MGUS differs from myeloma in that the amount of this paraprotein is less than 30 g/L (< 3g/dL) in MGUS.

2. In MGUS, the problematic cells, or plasma cells, are not as widespread in the bone marrow as they are in myeloma; in MUGUS plasma cells are less than 10 percent of the total on bone marrow examination.

SMOLDERING MYELOMA

Myeloma is often discovered through routine blood work when patients are being evaluated for something unrelated. Smoldering or indolent myeloma is a slowly progressing, early form of the disease. Although levels of the antibody-producing plasma cells in the bone marrow and/or high levels of M-protein may be present, there is still no significant damage to the bones or kidneys.

In smoldering, asymptomatic myeloma:

1. The amount of paraprotein is more than 30 g/L (< 3g/dL).

2. Plasma cells are more than 10 percent on bone marrow examination.

The major difference between smoldering myeloma and full-blown multiple myeloma is the absence of myeloma-related organ or tissue impairment.

MULTIPLE MYELOMA

Symptomatic, or active myeloma has the increased number of plasma cells in the bone marrow, the M- protein detected in the blood or urine—and also the resulting organ damage. Multiple myeloma requires treatment. In some cases of multiple myeloma, the cancerous cells will collect in a single bone and form a tumor called a plasmacytoma.

Signs and symptoms of multiple myeloma can vary and may include:

  • Bone pain, especially in the spine or chest
  • Nausea, constipation, loss of appetite, weight loss
  • Mental fogginess, confusion, fatigue
  • Frequent infections and fevers
  • Weakness or numbness in the legs
  • Excessive thirst, frequent urination

Symptomatic myelomas are further classified by the types of immunoglobulin proteins found in the blood. Immunoglobulins contain different parts – called heavy chains and light chains. Antibodies are named by the type of heavy chain part they contain (G, A, M, D, or E).

  • The most common M-protein in myeloma is the IgG type.
  • Less common are IgA myelomas.
  • IgD and IgE myelomas are extremely unusual.
  • Overproduction of IgM is a rare condition called Waldenstrom's macroglobulinemia.

Some types of myelomas produce an incomplete immunoglobulin of light chains only. These are called light chain myelomas. Light chain proteins are also referred to as Bence-Jones proteins. When Bence-Jones proteins are in the urine, they accumulate in the kidneys and cause damage.

There also some rare diseases in which the cancerous cells overproduce heavy chains only. These are called heavy chain disease and may or may not share characteristics with myeloma. Approximately 1 percent of myelomas are called non-secretory myeloma. In these patients, the production of M-proteins or light chains is not enough to be detected in the blood or urine. Special testing is required to identify disease in these patients.

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