AXONAL NEUROPATHY ASSOCIATED WITH MONOCLONAL GAMMOPATHY OF UNDETERMINED SIGNIFICANCE

Objective-The neuropathy associated with monoclonal gammopathy of unde termined significance (MGUS) is typically a predominantly demyelinatin g process that may have additional features of axonal degeneration. Si xteen patients with MGUS and a pure or predominantly axonal neuropathy are reported and compared with 20 consecutive patients with demyelina ting neuropathy and MGUS who were seen during the same period. Methods -Retrospective review of a consecutive series of patients with neuropa thy and MGUS evaluated during a five year period. Results-The axonal g roup had mild, symmetric, slowly progressive, predominantly sensory ne uropathy, usually limited to the legs. There were no differences in th e age of onset or duration of symptoms at the time of presentation, in itial symptoms, or the severity of weakness between the axonal and dem yelinating cases. However, the axonal process was associated with less vibration and proprioceptive loss, did not include leg ataxia (presen t in 55% of patients with demyelinating type), less often had generali sed areflexia (19% v 70%), IgM gammopathy (19% v 80%), and anti-MAG an tibodies (0% v 40%), and had lower CSF protein concentrations (mean, 4 9 v 100 mg/dl). The illness was also generally milder with less disabi lity (mean Rankin score 2.1 v 2.8). Fewer patients with axonal neuropa thy improved with immunomodulating therapy (27% v 75%). Conclusion-The re is an axonal neuropathy associated with MGUS that is clinically and electrophysiologically distinct from the more typical demyelinating p attern.