Myeloma is a
malignancy of plasma cells. Plasma cells produce immunoglobulins, which are commonly called antibodies. There are thousands of different antibodies, each consisting of pairs of heavy and light chains. Antibodies are typically grouped into five classes: IgA, IgD, IgE, IgG, and IgM. When someone has myeloma, a malignant clone, a rogue plasma cell, reproduces in an uncontrolled fashion, resulting in overproduction of the specific antibody the original cell was generated to produce. Each type of antibody has a different number of light chain and heavy chain pairs. As a result, there is a characteristic normal distribution of these antibodies in the blood by molecular weight. When there is a malignant clone, there is usually overproduction of a single antibody, resulting in a "spike" on the normal distribution (sharp peak on the graph), which is called an M spike (or monoclonal spike). People will sometimes develop a condition called MGUS (
Monoclonal gammopathy of undetermined significance), where there is overproduction of one antibody but the condition is benign (non-cancerous). An explanation of the difference between multiple myeloma and MGUS can be found in the International Myeloma Foundation's Patient Handbook. and Concise Review Detection of paraproteins in the
urine or
blood is most often associated with MGUS, where they remain "silent", and
multiple myeloma. An excess in the blood is known as
paraproteinemia. Paraproteins form a narrow band, or 'spike' in
protein electrophoresis as they are all exactly the same protein. Unlike normal immunoglobulin antibodies, paraproteins cannot fight infection.
Serum free light-chain measurement can detect free light chains in the blood. Monoclonal free light chains in the serum or urine are called
Bence Jones proteins. ==Interpretation upon detection==