Motor neuron disease and serum monoclonal proteins: poor response to treatment of the paraproteinemia.

An association between motor neuron disease (MND) and paraproteinemia has been previously reported. In a retrospective study, we found that 13 of 117 (11%) patients with MND who had serum protein electrophoresis studies were found to have a serum M-protem. Eleven of 13 patients had probable or definite amyotrophic lateral sclerosis (ALS), Of the 11 patients with ALS, six were treated with immunotherapy or chemotherapy. Subjective or objective neurologic improvement was not identified in any. Our data support an association between MND and paraproteinemia, but response to treatment of the paraproteinemia was disappointing. Searching for an M-protein in probable or definite ALS may not be therapeutically relevant.