Monoclonal gammopathy of undetermined significance occurs when plasma cells in your bone marrow produce an abnormal protein called monoclonal protein (M protein). Plasma cells are a type of white blood cell. They are found in your bone marrow. Plasma cells produce some of the antibodies that help your body fight infection.

In the majority of people with monoclonal gammopathy of undetermined significance, the protein isn't harmful. But when too much M protein accumulates, it crowds out healthy cells in your bone marrow and can damage other tissues in your body.

Genetic changes appear to play a role in monoclonal gammopathy of undetermined significance, as do environmental triggers.

May. 17, 2013