Monoclonal gammopathy of uncertain significance
| Monoclonal gammopathy of undetermined significance | |
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| Synonyms | monoclonal gammopathy of unknown significance, (monoclonal gammopathy of renal significance) |
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| Schematic representation of a normal protein electrophoresis gel. A small spike would be present in the gamma (γ) band in MGUS | |
| Classification and external resources | |
| ICD-10 | D47.2 |
| ICD-9-CM | 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 an abnormal immunoglobin protein (known as a paraprotein) is found in the blood during standard laboratory blood tests. MGUS 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, and it has no symptoms or major problems. However, multiple myeloma develops at the rate of about 1.5% a year, so doctors recommend monitoring it yearly.
The progression from MGUS to multiple myeloma usually involves several steps. In rare cases, it may also be related with a slowly progressive symmetric distal sensorimotor neuropathy.
People with monoclonal gammopathy generally do not experience signs or symptoms. Some people may experience a rash or nerve problems, such as numbness or tingling. Severe renal disease has also been found in a subset of those with monoclonal gammopathy. MGUS is usually detected by chance when the patient has a blood test for another condition or as part of standard screening.
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.
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