Monoclonal Immunoglobulin Associated with Monoclonal Free Light Chains Invisible on Capillary Electrophoresis.

BACKGROUND

We report the case of a monoclonal immunoglobulin of IgM Lambda isotype associated with monoclonal lambda-type free light chains not detected by capillary electrophoresis but identified by immunofixation.

METHODS

Capillary electrophoresis showed hypoproteinemia and an inflammatory syndrome. The IF realized on Hydrasys 2 Scan Focusing Sebia® reveals an IgM monoclonal band and two monoclonal bands in the total lambda. A second IF is performed using anti IgM, anti IgD, anti IgE and anti-total and -free lambda light chains as antisera. It reveals the presence of a monoclonal protein isotype IgM Lambda with free light chains. In view of these discordant results, an immunosubtraction was performed on the same sample showing no abnormality.

RESULTS

Our patient has a monoclonal IgM Lambda with lambda monoclonal free light chains all masked on capillary electrophoresis and therefore not detected.

CONCLUSIONS

Capillary electrophoresis techniques are incrementally becoming the techniques of choice in medical laboratories as a replacement for gel electrophoresis, due to their automation and better sensitivity. However, in some cases, a monoclonal immunoglobulin may not be detected by capillary technique and may cause an inaccurate interpretation.