Comparison of IgM-MGUS and IgG-MGUS polyneuropathy

To compare the clinical and electrodiagnostic features and response to treatment in patients with IgM-MGUS and IgG-MGUS associated polyneuropathy.

Retrospective review of 34 consecutive patients with MGUS associated neuropathy evaluated over 5 years.

There were 19 patients with IgM-MGUS and 15 with IgG-MGUS. There were no differences in age, duration of symptoms, or distribution of motor and sensory symptoms or signs. IgM-MGUS patients had prolonged distal latencies of the median and ulnar motor potentials, greater slowing of the peroneal nerve conduction velocity and more often absent ulnar sensory potentials. Half of the patients in both groups improved following immunotherapy.

IgM-MGUS patients had more severe demyelination on the nerve conduction studies, but there were no clinical features that differentiated the 2 groups. IgM and IgG-MGUS patients improved with plasma exchange and other immune therapies. Anti-MAG antibodies failed to distinguish a subgroup of patients with IgM-MGUS neuropathy.