Occurrence of Double Monoclonal Bands on Protein Electrophoresis: An Unusual Finding

Various techniques of protein electrophoresis are used for detection of monoclonal proteins/paraproteins in serum and/or urine of patients with monoclonal gammopathies. These are detected as the so-called 'M' bands (monoclonal bands) on serum protein electrophoresis and/or immunofixation electrophoresis. In most cases, a single M-band is detected. However, more than one M-band can be detected in the samples of a minor proportion of patients. This condition is termed as 'double gammopathy' or 'biclonal gammopathy'. A knowledge of such an unusual occurrence is essential for recognition and appropriate interpretation of this entity.

Heavy chain diseases

Heavy chain diseases (HCDs) are rare B-cell lymphoplasma-cell proliferative disorders characterized by production of truncated monoclonal immunoglobulin heavy chains without associated light chains. HCDs involving the three main immunoglobulin classes have been described; alpha-HCD is the most common and has the most uniform presentation, gamma- and mu-HCDs have variable clinical presentations and histopathologic features. HCDs can be thought of as variant types of non-Hodgkin lymphoma: alpha-HCD presents as an extranodal marginal-zone lymphoma of mucosa-associated lymph-node tissue, gamma-HCD as lymphoplasmacytoid non-Hodgkin lymphoma, and mu-HCD as small lymphocytic non-Hodgkin lymphoma or chronic lymphocytic leukemia. Diagnosis of HCD requires documentation of a deleted immunoglobulin heavy chain without a bound light chain in the serum or urine. Prognosis is variable, and no standardized effective treatment programs are available except for alpha-HCD, which in its early stage may respond to antibiotics.

Heavy chain disease

The heavy chain diseases (HCDs) are rare B-cell malignancies that are distinguished by the production of a monoclonal immunoglobulin heavy chain (HC) without an associated light chain by the malignant B-cells. There are three types of HCD defined by the class of immunoglobulin (Ig) HC produced: IgA (alpha-HCD), IgG (gamma-HCD), and IgM (mu-HCD). Alpha-HCD is the most common and occurs most commonly as intestinal malabsorption in a young adult from a country bordering the Mediterranean Sea. Treatment consists of antibiotics and improved nutrition and hygiene. Surgery is occasionally required for patients with bulky masses at risk for bowel perforation. If there is no response to antibiotics or if aggressive non-Hodgkin's lymphoma (NHL) is diagnosed, the patient should be treated with chemotherapy. Gamma- and mu-HCD are rare and essentially are found in patients with a B-cell NHL that produces an abnormal Ig heavy chain. These patients occasionally may be diagnosed with a monoclonal gammopathy of undetermined significance (MGUS). Patients with MGUS with NHL should be administered chemotherapy. Screening the serum and urine of patients with lymphoplasmacytoid NHL would likely identify more patients with gamma- or mu-HCD.

Procedures for the evaluation of monoclonal immunoglobulins

A wide variety of techniques are available for the screening, characterization, and quantification of monoclonal proteins. These techniques vary in regard to the expense, skill and intensity of labor involved, and sensitivity for detection of low levels of monoclonal proteins or of those with unusual migration. Detection of monoclonal proteins requires the use of high-resolution electrophoresis (either gel-based or capillary) and immunofixation (or immunosubtraction). Immunoelectrophoresis is not recommended. Urine for detection of monoclonal free light chains should be from 24-hour samples, and the aliquot should be concentrated at least 100-fold prior to electrophoresis and immunofixation. Dipstick and sulfosalicylic acid techniques are not sensitive enough to detect small quantities of monoclonal free light chains and should not be used as screening tests for this purpose.