A myeloma protein is an abnormal antibody (immunoglobulin) or (more often) a fragment thereof, such as an immunoglobulin light chain, that is produced in excess by an abnormal monoclonal proliferation of plasma cells, typically in multiple myeloma. Other terms for such a protein are M protein, M component, M spike, spike protein, or paraprotein. This proliferation of the myeloma protein has several deleterious effects on the body, including impaired immune function, abnormally high blood viscosity ("thickness" of the blood), and kidney damage.