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A Case of Waldenstrom Macroglobulinemia with Temporary Appearance of 7S IgM Half Molecule by Mayumi Imoto, Koji Yoshida, Yasuhiro Maeda, Ken-Ichi Nakae, Masatoshi Kudo, Ikunosuke Sakurabayashi, Toshiyuki Yamada, Toshinori Kamisako

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.

DOI: 10.7754/Clin.Lab.2017.170106