Typing of Four Cases of Monoclonal Gammopathy: A Revival of Immunosubstraction Role

Abstract

Monoclonal gammopathy of undetermined significance (MGUS) is characterized by increased production of an immunoglobuling (Ig) from a clone of plasma cells and is a pre-malignant disorders in subjects older than 50 years. The prevalence of MGUS in Caucasian population is still not determined. MGUS is characterized by the presence of a monoclonal-protein(M-protein) (IgG and IgA) lower than 30 g/L, bone marrow plasma cell percentage lower than 10%, and absence of clinical signs related to multiple myeloma (MM). MGUS can be responsible for damage to organs through the production of toxic M proteins that may have autoantibody activity or deposit pathologically in the organ tissues. Many techniques are available for the characterization of M-proteins. These techniques can involve different expenses, skills, labor time, and sensitivity in detecting monoclonal proteins also at low-level. Detection of M-proteins needs of assays based on high-resolution electrophoresis and im-munofixation (or immunosubtraction). We show suggestive clinical cases where the subjects involved had not an apparent disease but they showed an interesting pattern in electrophoresis. All cases were investigated by capillary’s electrophoresis and immunofixation to confirm or not the clinical suspect, and then if the immunofixation is not exhaustive, additionally immunosubstraction is done. However in some cases, the interpretation of the peaks is not so easy. Clinical and scientific data provided evidences that immunofixaction technique can fail the identification of monoclonal components. In that cases, we opted for the immunosubtraction method as a third level test, in that cases when immunofixation failed the identification of a monoclonal protein.