Monoclonal gammopathy of undetermined significance
Monoclonal gammopathy of undetermined significance Classification and external resources
Schematic representation of a normal protein electrophoresis gel. A small spike would be present in the gamma (γ) band in MGUS
ICD-10 D47.2 ICD-9 273.1 ICD-O: 9765/1 DiseasesDB 1341 eMedicine med/1495 MeSH D008998
Monoclonal gammopathy of undetermined significance (MGUS, unknown or uncertain may be substituted for undetermined), formerly benign monoclonal gammopathy, is a condition in which a paraprotein is found in the blood during standard laboratory tests. It resembles multiple myeloma and similar diseases, but the levels of antibody are lower, the number of plasma cells (white blood cells that secrete antibodies) in the bone marrow is lower, it has no symptoms or problems, and no treatment is indicated. However, multiple myeloma develops at the rate of about 1-2% a year, so doctors recommend monitoring it yearly. In rare cases, it may also be related with a slowly progressive symmetric distal sensorimotor neuropathy.
Increased serum protein with M spike. Other typical features seen in multiple myeloma are absent, such as hypercalcemia, lytic bone lesions, Bence Jones proteinuria, and AL amyloid. Commonly seen in elderly.
MGUS is a common, age-related medical condition characterized by an accumulation of bone marrow plasma cells derived from a single abnormal clone. Patients may be diagnosed with MGUS if they fulfill the following three criteria:
- A monoclonal paraprotein band less than 30 g/L (< 3g/dL);
- Plasma cells less than 10% on bone marrow examination; and
- No evidence of bone lesions, anemia, hypercalcemia, or renal insufficiency related to the paraprotein.
Several other illnesses can present with a monoclonal gammopathy, and the monoclonal protein may be the first discovery before a formal diagnosis is made:
- Multiple myeloma
- Chronic lymphocytic leukemia
- Non-Hodgkin Lymphoma, particularly Splenic marginal zone lymphoma and Lymphoplasmocytic lymphoma
- Hepatitis C
- Connective tissue disease such as lupus
- Immunosuppression following organ transplantation
- Waldenström macroglobulinemia
- Guillain-Barre syndrome
Pathologically, the lesion in MGUS is in fact very similar to that in multiple myeloma. There is a predominance of clonal plasma cells in the bone marrow with an abnormal immunophenotype (CD38+ CD56+ CD19−) mixed in with cells of a normal phenotype (CD38+ CD56− CD19+); in MGUS, on average more than 3% of the clonal plasma cells have the normal phenotype, whereas in multiple myeloma, less than 3% of the cells have the normal phenotype. What causes MGUS to transform into multiple myeloma is as yet unknown.
At the Mayo Clinic, MGUS transformed into multiple myeloma or similar myeloproliferative disorder at the rate of about 1-2% a year, or 17%, 34%, and 39% at 10, 20, and 25 years, respectively, of follow-up—among surviving patients. However, because they were elderly, most patients with MGUS died of something else and did not go on to develop multiple myeloma. When this was taken into account, only 11.2% developed myeloproliferative disorders.
Kyle studied the prevalence of myeloma in the population as a whole (not clinic patients) in Olmsted County, Minnesota. They found that the prevalence of MGUS was 3.2% in people above 50, with a slight male predominance (4.0% vs. 2.7%). Prevalence increased with age: of people over 70 up to 5.3% had MGUS, while in the over-85 age group the prevalence was 7.5%. In the majority of cases (63.5%), the paraprotein level was <1 g/dl, while only a very small group had levels over 2 g/dl. A study of monoclonal protein levels conducted in Ghana showed a prevalence of MGUS of approximately 5.9% in African men over the age of 50.
In 2009, prospective data demonstrated that all or almost all cases of Multiple Myeloma are preceded by MGUS. In addition to multiple myeloma, MGUS may also progress to Waldenström's macroglobulinemia, primary amyloidosis, B-cell lymphoma, or chronic lymphocytic leukemia.
The protein electrophoresistest should be repeated annually, and if there is any concern for a rise in the level of monoclonal protein, then prompt referral to a hematologist is required. The hematologist, when first evaluating a case of MGUS, will usually perform a skeletal survey (X-rays of the proximal skeleton), check the blood for hypercalcemia and deterioration in renal function, check the urine for Bence Jones protein and perform a bone marrow biopsy. If none of these tests are abnormal, a patient with MGUS is followed up once every 6 months to a year with a blood test (serum protein electrophoresis).
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- Advances in understanding monoclonal gammopathy of undetermined significance as a precursor of multiple myeloma.
Brendan W. Weiss & Michael Kuehl. Expert Rev Hematol. 3(2), 165-174 (2010)
- New criteria to identify risk of progression in monoclonal gammopathy of uncertain significance and smoldering multiple
myeloma based on multiparameter flow cytometry analisis of bone marrow plasma cells. Ernesto Perez-Persona et al. Blood, 1 October 2007. Vol 110. N 7, 2586–2592
- Seven-year median time to progression with thalidomide for smoldering myeloma: partial response identifies subset requiring
earlier salvage therapy for symptomatic disease. Bart Barlogie et al. Blood 15 October 2008. Vol 112. N 8, 3122-3125
- Proposal and Validation of Prognostic Scoring Systems for IgG and IgA Monoclonal Gammopathies of Undetermined Significance.
Francesca Rossi et al. Clin Cancer Res 2009; 15 (13), July 1, 2009, 4439-4445
- The potential Role of Curcumin in Patients with Monoclonal Gammopathy of Undetermined Significance-Its effect on
Paraproteinemia and the Urinary N-Telopeptide of Tyoe I Collagen Bone Turnover Marker. Terry Golombick et al. Clin Cancer Res 2009; 15(18), September 15, 2009, 5917-5922
- Prevention of Progression in Monoclonal Gammopathy of Undetermined Significance. S. Vincent Rajkumar. Clin Cancer
Res 2009; 15(18), September 15, 2009, 5606-5608
- Monoclonal Gammopathy of Undetermined Significance: a consensus statement. James R. Berenson et al. Brit J Hematol, 2010, 150, 28-38
- Monoclonal Gammopathy of Undetermined Significance (MGUS) and Smoldering (asymptomatic) Multiple Myeloma: IMWG consensus
perspectives risk factors for progression and Guidelines for monitoring and management. R A Kyle et al. Leukemia (2010, 1-7
Immune disorders, Immunoproliferative immunoglobulin disorders (D89, 273) PCDs/PP Other hypergammaglobulinemia Hematological malignancy/leukemia histology (ICD-O 9590–9989, C81–C96, 200–208)
Lymphoid/Lymphoproliferative, Lymphomas/Lymphoid leukemias (9590–9739, 9800–9839)By development/
markerALL (Precursor B acute lymphoblastic leukemia/lymphoma)CD5+CD22+see immunoproliferative immunoglobulin disordersBy infectionBy development/
CD30-: Non-mycosis fungoides CD30− cutaneous large T-cell lymphoma · Pleomorphic T-cell lymphoma · Lymphomatoid papulosis type BCD30+: CD30+ cutaneous T-cell lymphoma · Secondary cutaneous CD30+ large cell lymphoma · Lymphomatoid papulosis type AOther peripheralBy infectionHTLV-1 (Adult T-cell leukemia/lymphoma)NK cell/
(most CD56)Aggressive NK-cell leukemia · Blastic NK cell lymphomaT or NKLymphoid+myeloid
Cutaneous lymphoid hyperplasiaCutaneous lymphoid hyperplasia with bandlike and perivascular patterns · Cutaneous lymphoid hyperplasia with nodular pattern · Jessner lymphocytic infiltrate of the skin
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