Table 1 International Myeloma Working Group Diagnostic Criteria for Multiple Myeloma and Related Plasma Cell Disorders.

From: Smoldering multiple myeloma current treatment algorithms

Disorder

Disease Definition

IgM Monoclonal gammopathy of undetermined significance (IgM MGUS)

All 3 criteria must be met:

 • Serum IgM monoclonal protein <3 gm/dL

 • Bone marrow lymphoplasmacytic infiltration <10%

 • No evidence of anemia, constitutional symptoms, hyperviscosity, lymphadenopathy, or hepatosplenomegaly that can be attributed to the underlying lymphoproliferative disorder.

Non-IgM monoclonal gammopathy of undetermined significance (MGUS)

All 3 criteria must be met:

 • Serum monoclonal protein (non-IgM type) <3 gm/dL

 • Clonal bone marrow plasma cells <10%a

 • Absence of end-organ damage such as hypercalcemia, renal insufficiency, anemia, and bone lesions (CRAB) that can be attributed to the plasma cell proliferative disorder

Light Chain MGUS

All criteria must be met:

 • Abnormal free light chain (FLC) ratio (<0.26 or >1.65)

 • Increased level of the appropriate involved light chain (increased kappa FLC in patients with ratio >1.65 and increased lambda FLC in patients with ratio <0.26)

 • No immunoglobulin heavy chain expression on immunofixation

 • Absence of end-organ damage that can be attributed to the plasma cell proliferative disorder

 • Clonal bone marrow plasma cells <10%

 • Urinary monoclonal protein <500 mg/24 h

Smoldering multiple myeloma

Both criteria must be met:

• Serum monoclonal protein (IgG or IgA) ≥3 gm/dL, or urinary monoclonal protein ≥500 mg per 24 h and/or clonal bone marrow plasma cells 10–60%

• Absence of myeloma defining events or amyloidosis

Multiple Myeloma

Both criteria must be met:

 • Clonal bone marrow plasma cells ≥10% or biopsy-proven bony or extramedullary plasmacytoma

 • Any one or more of the following myeloma defining events

  ◦ Evidence of end organ damage that can be attributed to the underlying plasma cell proliferative disorder, specifically:

   ▪ Hypercalcemia: serum calcium >0·25 mmol/L ( >1 mg/dL) higher than the upper limit of normal or >2·75 mmol/L ( >11 mg/dL)

   ▪ Renal insufficiency: creatinine clearance <40 mL per minute or serum creatinine >177 μmol/L ( >2 mg/dL)

   ▪ Anemia: hemoglobin value of >2 g/dL below the lower limit of normal, or a hemoglobin value <10 g/dL

   ▪ Bone lesions: one or more osteolytic lesions on skeletal radiography, computed tomography (CT), or positron emission tomography-CT (PET-CT)

  ◦ Clonal bone marrow plasma cell percentage ≥60%

  ◦ Involved: uninvolved serum free light chain (FLC) ratio ≥100 (involved free light chain level must be ≥100 mg/L and urine monoclonal protein level at least 200 mg per 24 h on urine protein electrophoresis)

  ◦ >1 focal lesions on magnetic resonance imaging (MRI) studies (at least 5 mm in size)

  1. Modified from Rajkumar SV, Dimopoulos MA, Palumbo A, et al. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma. Lancet Oncol 2014;15:e538–e548.
  2. aA bone marrow can be deferred in patients with low risk MGUS (IgG type, M protein <1.5 gm/dL, normal free light chain ratio), in patients with uncomplicated suspected IgM MGUS < 1.5 gm/dl, and in patients with light chain MGUS who have a serum FLC ratio <8, in whom there are no clinical features concerning for myeloma, macroglobulinemia, or amyloidosis.
Back to article page