Monoclonal gammopathy is present in a patient when a monoclonal protein (also referred as M protein or paraprotein) is identified in the patient’s serum, urine, or both. Monoclonal gammopathy may be of undetermined significance or due to myeloma or a B cell lymphoproliferative disorder producing this paraprotein. Multiple myeloma, a malignant disorder of bone marrow, is the most common form of myeloma.
This disease is called multiple myeloma because it affects multiple organs in the body. In multiple myeloma, plasma cells that proliferate at a low rate become malignant with a massive clonal expression resulting in a high rate of production of monoclonal immunoglobulin in the circulation. Monoclonal gammopathy of undetermined significance was first described in 1978 and is a precancerous condition affecting approximately 3% of people above age 50 years.