Monoclonal gammopathy of undetermined significance
| Monoclonal gammopathy of undetermined significance | |
| ICD-10 | D47.2 |
|---|---|
| ICD-9 | 273.1 |
| DiseasesDB | 1341 |
| eMedicine | med/1495 |
| MeSH | D008998 |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Monoclonal gammopathy of undetermined significance (MGUS, unknown or uncertain may be substituted for undetermined) or benign monoclonal gammopathy is a condition in which a low or non-quantifiable level of a monoclonal paraprotein is detected in the blood by means of protein electrophoresis. In addition, some patients develop a polyneuropathy (damage to peripheral nerves) or other problems related to the secreted antibody. MGUS is distinct from multiple myeloma, as described below.
Diagnosis
Patients may be diagnosed with MGUS if they fulfill the following three criteria:[1]
- A monoclonal paraprotein band less than 3 g/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.
Differential diagnosis
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
- AIDS
- Chronic lymphocytic leukemia
- Non-Hodgkin Lymphoma, particularly Splenic marginal zone lymphoma[2] and Lymphoplasmocytic lymphoma
- Hepatitis C
- Connective tissue disease such as lupus[3]
- Immunosuppression following organ tranplantation
- Waldenström macroglobulinemia
- Guillain-Barre syndrome[4]
Pathology
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+);[5][6] in MGUS, 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.[7] What causes MGUS to transform into multiple myeloma is as yet unknown.
Prognosis
MGUS may be considered a pre-malignant condition, given the possibility of transformation into multiple myeloma. However, because the condition tends to occur in the elderly, and because the rate of progression is slow, only a small proportion of people with MGUS go on to develop a haematological malignancy. In patients with MGUS, although the actuarial risk of myeloma at 25 years of follow-up is 30%, the actual risk (when competing causes of death are taken into account) is only 11%.[8]
The annual risk of progressing to multiple myeloma is around 1–2% a year. Kyle et al studied the prevalence of myeloma in a population-wide cohort 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.[9]
In addition to multiple myeloma, MGUS may also progress to Waldenström's macroglobulinemia, primary amyloidosis, B-cell lymphoma, or chronic lymphocytic leukemia.
Annual review
The protein electrophoresis test should be repeated annually, and if there is any concern for a rise in the level of monoclonal protein, then prompt referral to a haematologist is required. The haematologist, 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).
References
- ↑ International Myeloma Working Group (2003). "Criteria for the classification of monoclonal gammopathies, multiple myeloma and related disorders: a report of the International Myeloma Working Group". Br J Haematol. 121 (5): 749–57. PMID 12780789.
- ↑ Murakami H, Irisawa H, Saitoh T, Matsushima T, Tamura J, Sawamura M, Karasawa M, Hosomura Y, Kojima M (1997). "Immunological abnormalities in splenic marginal zone cell lymphoma". Am. J. Hematol. 56 (3): 173–8. PMID 9371530.
- ↑ Larking-Pettigrew M, Ranich T, Kelly R (1999). "Rapid onset monoclonal gammopathy in cutaneous lupus erythematosus: interference with complement C3 and C4 measurement". Immunol. Invest. 28 (4): 269–76. PMID 10454004.
- ↑ Czaplinski A, Steck A (2004). "Immune mediated neuropathies--an update on therapeutic strategies". J. Neurol. 251 (2): 127–37. PMID 14991345.
- ↑ Zhan F, Hardin J, Kordsmeier B, Bumm K, Zheng M, Tian E, Sanderson R, Yang Y, Wilson C, Zangari M, Anaissie E, Morris C, Muwalla F, van Rhee F, Fassas A, Crowley J, Tricot G, Barlogie B, Shaughnessy J (2002). "Global gene expression profiling of multiple myeloma, monoclonal gammopathy of undetermined significance, and normal bone marrow plasma cells". Blood. 99 (5): 1745–57. PMID 11861292.
- ↑ Magrangeas F, Nasser V, Avet-Loiseau H, Loriod B, Decaux O, Granjeaud S, Bertucci F, Birnbaum D, Nguyen C, Harousseau J, Bataille R, Houlgatte R, Minvielle S (2003). "Gene expression profiling of multiple myeloma reveals molecular portraits in relation to the pathogenesis of the disease". Blood. 101 (12): 4998–5006. PMID 12623842.
- ↑ Ocqueteau M, Orfao A, Almeida J, Bladé J, González M, García-Sanz R, López-Berges C, Moro M, Hernández J, Escribano L, Caballero D, Rozman M, San Miguel J (1998). "Immunophenotypic characterization of plasma cells from monoclonal gammopathy of undetermined significance patients. Implications for the differential diagnosis between MGUS and multiple myeloma". Am J Pathol. 152 (6): 1655–65. PMID 9626070.
- ↑ Bladé J (2006). "Clinical practice. Monoclonal gammopathy of undetermined significance". N Engl J Med. 355 (26): 2765–70. PMID 17192542 Abstract.
- ↑ Kyle RA, Therneau TM, Rajkumar SV, Larson DR, Plevak MF, Offord JR, Dispenzieri A, Katzmann JA, Melton LJ 3rd. (2006). "Prevalence of monoclonal gammopathy of undetermined significance". N Engl J Med. 354: 1362–9. PMID 16571879. Unknown parameter
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