Peripheral neuropathy associated with IgM monoclonal gammopathy: Correlations between M-protein antibody activity and clinical/electrophysiological features in 40 cases

Forty cases of polyneuropathy associated with IgM monoclonal gammopathy were retrospectively studied to investigate the relevance of clinical and electrophysiological features to M‐protein antibody activity. There were 26 men and 14 women; mean age was 65 ± 11.7 years at the time of the study. Thirty‐nine patients had a symmetrical polyneuropathy, of whom 13 had a predominantly sensory and 17 a purely sensory neuropathy (i.e., 30 sensory neuropathies). The remaining patient had a multifocal mononeuropathy. Electrophysiological studies allowed the polyneuropathies to be classified as demyelinating in 33 cases (82.5%) and axonal in 6 cases. Antibody studies disclosed anti‐MAG antibodies in 65% and anti‐SGPG antibodies in 82.5% of patients. Anti‐MAG antibodies were associated with only demyelinating polyneuropathies. Anti‐SGPG antibodies were found in 91% of demyelinating polyneuropathies and 50% of axonopathies. In addition, anti‐MAG/SGPG antibody activity was significantly correlated with the subgroup of sensory neuropathies (P < 0.01). Last, antisulfatide antibodies were found at significant titers in 18 cases, and their presence was significantly correlated with anti‐MAG/SGPG antibody activity, but not with some clinical/electrophysiological features. © 1998 John Wiley & Sons, Inc. Muscle Nerve, 21: 55–62, 1998.