A Case of Waldenstrom Macroglobulinemia with Temporary Appearance of 7S IgM Half Molecule.

BACKGROUND

We encountered a rare case of Waldenstrom macroglobulinemia with temporary appearance of 7S IgM half molecule and with monoclonal proteins binding to agarose gel.

METHODS

The patient's serum and urine were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. The N-terminal amino acid sequences of the IgM with abnormal mass (68 kDa) were determined and compared with those of known immunoglobulin.

RESULTS

The 68 kDa IgM consisted of a defective μ chain (36 kDa) and an intact κ chain. N-terminal amino acid sequence analysis demonstrated that the defective μ chain had the variable region of IgM. The agarose gel-binding ability of the IgM-κ M-protein was lost after reduction or alkaline treatment of serum.

CONCLUSIONS

The 7S half molecule IgM in the present case may miss a large part of the constant region of the µ chain.