More Myeloma Overview
Other complications of myeloma may include the following:
- Cryoglobulinemia: People with this rare condition produce a protein that precipitates, or falls out of solution, when the blood is exposed to cold temperatures.
- Amyloidosis: This rare complication occurs mostly in people whose myeloma produces the light chain components of immunoglobulins. The light chains combine with other substances in the blood to form a sticky protein called amyloid, which impairs the function of whichever organ in which it may accumulate.
Different types of myeloma are classified by the type of immunoglobulin produced by the abnormal plasma cells. Immunoglobulins (Ig) are made up of two components: light chains and heavy chains and further classified by the type of light (kappa or lambda) or heavy (alpha [IgA], gamma [IgG], mu [IgM], delta [IgD], and epsilon [IgE]) chains.
- The most common monoclonal protein in myeloma is the IgG type. This means that the immunoglobulin is comprised of two IgG heavy chains and two light chains, either two kappa or two lambda. When the abnormal M protein is identified in myeloma, it is most often an IgG kappa type. However, any other combination is possible.
- Less common, but still prevalent, are IgA-producing myeloma cells.
- IgM myeloma is much less common.
- IgD and IgE myelomas are very rare.
- Some myelomas produce an incomplete immunoglobulin consisting of light chains only, known as Bence-Jones proteins, which are not identified by blood tests but readily identified in urine.
- Some rare diseases are associated with plasma cell overproduction of heavy chains only. These are referred to as heavy chain diseases. Heavy chain diseases may or may not be similar to myeloma in their characteristics.
- Nonsecretory myeloma occurs in about 1% of myelomas and represents malignant plasma cells that do not produce any immunoglobulin chains, heavy or light.
A plasma cell disorder related to myeloma is called monoclonal gammopathy of undetermined significance, or MGUS.
- People with MGUS produce small amounts of monoclonal protein, but they have none of the symptoms or complications of myeloma.
- MGUS is much more common than myeloma. The incidence of MGUS increases with age. It is uncommon in young individuals and reaches an incidence of approximately 3% in people aged 70 years and older.
MGUS is believed to be a premyeloma condition, although not all patients with MGUS develop myeloma. About 30% to 40% of people with MGUS, given sufficient time, may progress to develop myeloma.
Myeloma is the second most common blood cancer, but it is not a common cancer. The about 18,226 people were diagnosed with myeloma in the United States in 2010, almost equally distributed between men and women. About 11,428 Americans died of multiple myeloma in 2010.
- Myeloma is predominantly a cancer of older people. More than 75% of people diagnosed with myeloma in 2010 are aged 60 years or older.
- Myeloma is nearly twice as common in African Americans as in Americans of European, Hispanic, or Asian descent.
Clarence Sarkodee-Adoo, MD
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