Multifocal motor neuropathy. Immediate response to intravenous immunoglobulin.

Multifocal motor neuropathy, a rare insidious immune-mediated disorder, fea tures muscular weakness and atrophy, as well as arreflexia, due to nerve co nduction block and is often associated with the presence of anti-GM1 antibo dy. We report a patient with a nine-year history of progressive upper limb weakness, misdiagnosed as amyotrophic lateral sclerosis, who responded with in hours to intravenous immunoglobulin treatment with full recovery of musc le strength. This case highlights the need to search for conduction block i n patients with lower motor neuron involvement.