Monoclonal gammopathies include a group of diseases characterised by the clonal proliferation of plasma cells that produce a single type of light and/or heavy chain (monoclonal component) in excessive quantities.

Normal plasma cells produce immunoglobulins (Ig), or antibodies, substances that circulate in the blood to defend the body by attacking any foreign substances that enter the organism. Each Ig has two heavy chains: gamma (IgG), alfa (IgA), mu (IgM), delta (IgD), or epsilon (IgE), and two light chains (kappa or delta).

The concept of monoclonality implies that these neoplastic plasma cells produce a single type of heavy and/or light chain (for example, IgA-kappa, IgG-lambda; kappa light chain, etc.), and fail to produce the other normal immunoglobulins in sufficient quantity.

Excess immunoglobulins interfere with various properties of the blood, the normal functioning of the kidneys, and contribute to the development of infections (due to a deficit of the rest of the immunoglobulins).

Furthermore, an excess of plasma cells can injure the bones containing bone marrow (leading to bone pain and possible fractures).

 Monoclonal gammopathies include the following diseases:

• Monoclonal gammopathy of undetermined significance

• Multiple myeloma

• Waldenström macroglobulinemia

• Heavy chain diseases

• Primary amyloidosis