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Monoclonal gammopathy of undetermined significance
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.
Additional recommended knowledge
Patients may be diagnosed with MGUS if they fulfill the following three criteria:
Several other illnesses can present with a monoclonal gammopathy, and the monoclonal protein may be the first discovery before a formal diagnosis is made:
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, 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.
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%.
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.
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).
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Monoclonal_gammopathy_of_undetermined_significance". A list of authors is available in Wikipedia.|