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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.

We report the case of a patient with a severe, predominantly motor, demyelinating neuropathy associated with an IgM kappa biclonal gammopathy. Immunoblot studies showed IgM reactivity against MAG, and IgG reactivity against a peripheral nerve myelin-specific protein of approximately 35 kDa. Immunodetection by thin layer chromatography showed IgM reactivity towards GM1 and GD1b, as well as towards SGPG and SGLPG. This case illustrates the existence of overlapping syndromes among dysglobulinemic neuropathies, and points to an interaction of different autoantibodies in the pathogenesis of the nerve lesions.

In a study on 67 chronic neuropathies, we have shown that anti-GM1 antibodies are particularly frequent in multifocal motor neuropathies (MMN) with conduction blocks (17/24 cases). The detection of these antibodies by ELISA necessitates a confirmation by immunodetection on thin-layer chromatography, so as to distinguish the anti-GM1 antibodies present in MMN from natural antibodies which are polyreactive and of low affinity. There is no direct correlation between the anti-GM1 antibody titer, the immunosuppressive treatment and the clinical evolution. Nevertheless, the detection of high titer of anti-GM1 antibodies is an additional argument in favor of treatment by IVIg.

Twenty four patients with pure motor neuropathy are reported. The chronic motor involvement associated with fasciculations and cramps, mainly in the arms, led, in most patients, to an initial diagnosis of motor neuron disease. In some patients (nine of 24), there was no appreciable muscle atrophy. Tendon reflexes were often absent or weak. The finding of persistent multifocal conduction block confined to motor nerve fibres raises questions about the nature and the importance of this syndrome. Segmental reduction of motor conduction velocity occurred at the site of the block, but significant slowing of motor nerve conduction was not found outside this site. The response to intravenous IVIg treatment seems to be correlated with the absence of amyotrophy. Patients with little or no amyotrophy had an initial and sustained response to IVIg, and did not develop amyotrophy during the follow up study. They could be considered to have a variant of chronic inflammatory demyelinating polyneuropathy. Patients with pronounced amyotrophy independent of the disease duration did not respond as well to IVIg treatment, suggesting the existence of a distinct entity. Among the patients treated about two thirds who had an initial good response to IVIg had high or significant antiganglioside GM1 (anti-GM1) antibody titres, but there was no correlation between the high titres before treatment and long lasting response to IVIg treatment.

Intravenous human immune globulin (IVIg) has been proposed for the treatment of various peripheral neuropathies that are considered to be immunemediated. The results are reported of an open trial conducted in multifocal motor neuropathy and polyneuropathy associated with monoclonal gammopathy. Six cases with multifocal motor neuropathy, selected on clinical and electrophysiological criteria (four of six patients also had significantly high anti-GM1 titres), received IVIg monthly, at doses varying from 1.6 to 2.5 mg/kg, over three to 13 months. The initial response to treatment was dramatic in 3/6 cases (with improvement of at least two grades on the MRC scale in the five more severely affected muscles). The final evaluation showed a good result in 4/6 cases, but the conduction blocks were not significantly reduced. In 13 other cases with polyneuropathy associated with IgM monoclonal gammopathy of unknown significance, IVIg was of benefit, with improvement of at least one grade on the Prineas score, in 4/7 cases previously treated with immunosuppression and 2/3 cases not treated before IVIg. In the last group of four patients with polyneuropathy and IgG monoclonal gammopathy, IVIg was followed by clinical improvement in the two cases with a chronic demyelinating polyneuropathy.

We report on a 54-year-old man with a sensory-motor polyneuropathy associated with a biclonal IgM-kappa gammopathy, which reacted with the ganglioside GD1b. Examination of nerve biopsy specimens showed some reduction in the density of myelinated fibers and axonal degeneration with a loss of large fibers and a relative increase in the density of small fibers. Immunodetection on thin-layer chromatography of the glycolipid antigens showed strong reactivity of the patient's serum IgM-kappa with GD1b ganglioside and weak binding to GD1a. biclonal IgM antibodies did not react with GM1, asialo-GM1, GT1b, GD2, or GD3. Indirect immunofluorescence staining showed binding of IgM-kappa mainly in a crescent-like pattern on the internal side of myelin sheaths, which could correspond either to an enlarged periaxonal (adaxonal) space or to the internal mesaxon or to both. The immunostaining was abolished after absorption of the serum with GD1b.

CNS lesions were studied in polyneuropathy associated with IgM monoclonal gammopathy. Eleven out of 12 patients with IgM MGUS and one patient with Waldenstrom's disease had clinical and electrophysiological features indicating a demyelinating polyneuropathy. MRI showed CNS white matter lesions in two cases. Antibodies reacting against glycolipids present in CNS white matter were present in five cases, two of which had abnormal MRI. Central conduction times cortex-C7, obtained by magnetic stimulation, were prolonged in 3/8 patients, of which two patients had anti-CNS glycolipid antibodies.

In an experimental model of human African trypanosomiasis in sheep inoculated with Trypanosoma brucei brucei, we report an immunoglobulin reactivity towards central nervous system (CNS) glycolipids. Immunocharacterization of the glycolipid antigens was performed on thin-layer chromatography using peroxidase-labelled second antibody. An immunoreactivity against galactocerebroside antigens was observed in inoculated animals up to a dilution of 1:600 and was suppressed after immunoadsorption of sera on pure galactocerebrosides. As galactocerebroside antigen is responsible for demyelination in several experimental models, the relation between the important glycolipid immunoreactivity in inoculated sheep sera and the pathogenesis of CNS demyelination in African trypanosomiasis is suggested.