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Types of Myeloma

Myeloma is really not just one disease. It's a disease with several subtypes. In all cases of myeloma, abnormal plasma (blood) cells produce an unusually high number of only one of the types of antibodies – or immunoglobulins, as doctors often call them. The specific type of immunoglobulin that is overproduced by cancerous blood cells can vary from one person to the next, and determines the subtype of myeloma that the patient has. 

When plasma cells are exposed to foreign substances (antigens), they produce different antibodies called immunoglobulins. Immunoglobulins are made up of two types of protein:

  • Heavy chains (A, G, M, D and E)
  • Light chains (kappa [κ] or lambda [λ])

About 60-65% of all cases of myeloma involves the overproduction of immunoglobulins (Ig) made with "G" heavy chains (IgG). When too much of the same immunoglobulin is produced, this is referred to as monoclonoal protein (M-protein), monoclonal spike (M-spike), monoclonal peak (M-peak) or paraprotein.

  Subtypes of Myeloma

MGUS

(Monoclonal Gammopathy of Undertermined Significance)

  • Benign condition where M-protein (or paraprotein) is present, but there is no underlying disease (ie, no anemia, renal failure, excessive calcium in the blood or bone lesions)
  • Although there may be more abnormal plasma cells than usual in the bone marrow, they account for less than 10% of blood cells (the threshold for a diagnosis of myeloma)
  • Approximately 3.2% of the general population 50 years of age and older have MGUS. Of those, about 1% per year will develop active myeloma.
  • MGUS is usually monitored but not treated

Asymptomatic or Smouldering Myeloma

  • Transitional state between MGUS and active/symptomatic myeloma
  • M-protein is present in the blood and/or urine
  • Abnormal plasma cells may account for up to 10% of blood cells in the bone marrow
  • Still no symptoms or organ damage
  • Usually monitored but not treated
  • Supportive care may be given
Symptomatic or Active Myeloma

SLiM CRAB Criteria

The International Myeloma Working Group (IMWG) recently expanded the definition of active myeloma, to include any one of the following "SLiM" criteria to confirm the diagnosis of myeloma:

  • Sixty (60) percent or greater abnormal plasma cells on bone marrow examination
  • Light chain ratio (free, involved/uninvolved) of 100 or more in the blood (involved must be at least 100 mg/L)
  • MRI (magnetic resonance imaging) with more than one bone lesion (5 mm or greater)

Traditionally, the diagnosis of myeloma was based on:

  • M-protein is present in the blood or urine
  • Abnormal plasma cells account for 10% or more of blood cells in the bone marrow
  • Symptoms or complications may include one or more of the following "CRAB" criteria:
    • Calcium elevation in the blood
    • Renal insufficiency (kidney failure)
    • Anemia (low red blood count)
    • Bone disease (pain, increased risk of fractures, etc.)
  • Requires treatment

For more information, dowload the Multiple Myeloma Patient Handbook
Designed to provide educational support to patients, caregivers, families and friends, this handbook gives accurate, reliable, and clear information on myeloma. Topics cover its causes and effects, how it is diagnosed and the treatment options available in Canada.

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