Monoclonal proteins, or M proteins, are produced by a variety of white blood cells called plasma cells, explains Mayo Clinic. The condition known as monoclonal gammopathy of undetermined significance, or MGUS, refers to the presence of these abnormal proteins in the blood.
Monoclonal proteins are produced by plasma cells located in the bone marrow, explains University of Rochester Medical Center. Because they cause no symptoms, these proteins are typically discovered by accident. Monoclonal proteins are associated with MGUS. While the condition is not cancerous, it heightens the risk of developing serious blood and bone marrow conditions. However, the majority of individuals with MGUS never develop more dangerous conditions.
When monoclonal proteins are uncovered by accident, further tests have to be conducted, according to URMC. These tests are typically carried out on blood and, in some cases, urine using a technique known as electrophoresis. More testing may be carried out if preliminary checks uncovers signs of a more serious condition, such as Waldenstrom's macroglobulinemia, primary amyloidosis, plasma cell leukemia and multiple myeloma. Symptoms of some of the more serious conditions associated with MGUS include fatigue, weakness, recurring infections, headaches, weight loss, problems with vision, anemia and low red blood cell counts.