• We studied ten patients with IgM monoclonal gammopathies. Five had M proteins that reacted with myelin-associated glycoprotein (MAG) and five had no recognizable antinerve activity. The neuropathy in the MAG-reactive patients was homogeneous by clinical and laboratory analysis, while the neuropathy in the MAG-nonreactive patients varied considerably. Both groups responded well to immunosuppressive therapy, which lowered the concentration of the serum M protein. The homogeneity of the MAG-reactive patients and their response to sustained lowering of the M protein levels support the concept that the IgM M protein directly damages nerve fibers and is the proximate cause of the polyneuropathy.
Kelly JJ, Adelman LS, Berkman E, Bhan I. Polyneuropathies Associated With IgM Monoclonal Gammopathies. Arch Neurol. 1988;45(12):1355–1359. doi:10.1001/archneur.1988.00520360073015
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