[Anti-MAG paraproteinemic demyelinating polyneuropathy: a clinical, biological, electrophysiological and anatomopathological descriptive study of a 13-patients' cohort].

INTRODUCTION

Polyneuropathies associated with IgM paraproteinemia and anti-myelin associated glycoprotein (MAG) antibodies (MAG-PN) have to be differentiated from chronic inflammatory demyelinating polyneuropathies.

METHODS

In a retrospective study, we have analyzed clinical, electrophysiological, biological and pathological data from MAG-PN patients.

RESULTS

Seven male and six female patients were followed in the department for a mean 2 years (0.5-6.5 years). Mean age at diagnosis was 61 years (44.5-85.5 years). Patients had symmetrical bilateral paresthesia (11/13) and hypoesthesia (11/13) prominent in the lower limbs. Nine patients developed gait ataxia and four patients had moderate distal weakness in the lower limbs. Mean Overall Neuropathy Limitation Scale was 2.3 (0-5). Nerve conduction study showed demyelinating features though delayed distal motor latency on median (206 % of normal value) and ulnar nerves (150% of normal value). Seven out of thirteen patients had at least two nerves with terminal latency index below 0.25. IgM paraproteinemia was of undetermined significance in ten cases and three patients had non-Hodgkin lymphoma. IgM deposits and widening of the peripheral myelin were observed in 5/7 sural nerve biopsies. Anti-MAG antibodies were detected in the sera of all patients using enzyme-linked immunosorbent assay and in 8/12 patients using western blot analysis.

CONCLUSIONS

MAG-PN have distinctive clinical, electrophysiological and pathological features. It is a chronic, slowly progressive, predominantly sensory and ataxic neuropathy. Disability is usually moderate. Electrophysiological study shows distal demyelinating process and is highly suggestive of MAG-PN in more than one half of our patients. Several techniques may detect anti-MAG antibodies, they have to be associated to improve sensitivity and specificity of the test.