IgG monoclonal paraproteinaemia and peripheral neuropathy.

Five patients with peripheral neuropathy and benign IgG monoclonal paraproteinemia are reported, all of whom had a sensorimotor neuropathy with a remitting and relapsing course. The serum paraprotein level did not correlate with the patient's clinical status. Electrophsyiological studies showed marked slowing of conduction velocity and conduction block in four of the patients and mild slowing in the other. Sural nerve biopsies demonstrated a demyelinating neuropathy with inflammatory cell infiltrates in each of the five patients. Three of the patients had evidence of myelin/Schwann cell reactivity on immunofluorescence studies and in all nerves dense expression of major histocompatability complex class I and II molecules was evident within the endoneurium, on invading mononuclear cells, endothelial cells and Schwann cells. All the patients responded to treatment, plasmapheresis being particularly effective. Four patients have achieved prolonged remissions after all treatment had ceased. These five cases of peripheral neuropathy and IgG paraproteinaemia were identical in their clinical, electrophysiological and pathological features to patients with chronic inflammatory demyelinating polyneuropathy.