Polyneuropathy associated with IgM monoclonal gammopathy: a review. Clinical, electrophysiological and pathological features.

Polyneuropathy associated with IgM monoclonal gammopathy has been documented first for Waldenstrom's disease, then for IgM monoclonal gammopathy of undetermined significance (MGUS). The usual clinical aspect is a chronic symmetric predominantly sensory polyneuropathy, occurring insidiously in elderly patients. Tremor and ataxia are characteristic findings, but their mechanism is unclear. The electrophysiological and pathological features are consistent with a primary demyelination with secondary axonal loss. Monoclonal IgM level is frequently low in MGUS cases and the light chain is Kappa in most of the cases. The IgM M-protein is shown to bind to myelin-associated-glycoprotein (MAG) and/or other antigens of the peripheral nerve myelin in most of the cases. The course of the polyneuropathy is usually slowly progressive. Some other clinical aspects of peripheral neuropathy associated to IgM monoclonal gammopathy have been reported. Recently the attention has been directed towards motor neuron diseases (MND) associated to IgM MGUS, but the significance of this association remains unclear.