When an abnormal protein (band or peak) is detected, additional tests are done to identify the type of protein (immunotyping).

Possible monoclonal protein (M-protein) present.

A variety of conditions are related to M proteins:

MGUS (monoclonal gammopathy of undetermined significance). If you have this condition, you have both healthy plasma cells and abnormal ones. The abnormal plasma cells make M proteins that show up in your blood. Most of the time, MGUS doesn't cause any problems or symptoms. But for some people, MGUS turns into a harmful condition, such as multiple myeloma or lymphoma.

Smoldering multiple myeloma. This is the stage between MGUS and myeloma. There are more abnormal plasma cells and M proteins in the blood. Smoldering multiple myeloma usually doesn't cause any symptoms.

Multiple myeloma. When plasma cells are cancerous and grow out of control, it's called multiple myeloma. These cancer cells build up in the bone marrow and crowd out healthy cells. They also make M proteins. Higher levels of M protein in the blood can lead to complications.

Waldenstrom's macroglobulinemia. This cancer affects small lymphocytes (white blood cells). These cancerous cells make M proteins. A buildup of these proteins can thicken the blood and lead to symptoms, such as fatigue and weight loss.